Welcome all 928 forum refugees!
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By Crumpler
#10120
Well, not great success with the DIY SC. Running well and temps and wideband readings looked good.
I drove it down to the pro tuner I use. I dropped it off with a plan of a basic safe tune. Some may remember it’s an FMU set up and no knock detection right now.

They called today, and told me it did not go swimmingly on the dyno.
Initial 1.8 boost and stayed there, flatlined. No linear boost readings. I haven’t seen the curve, but he said it dropped 70 hp since the last runs — that were NA with s300 chips.
I asked about pulley sizes, but the consensus was don’t bother, if it’s not a linear increase in boost, then it’s a sick supercharger.

Sooooooo. While it looked like a cool build, the old off brand SC is exactly that, and probably worth about what I paid for it.
I guess I will pull the kit off and try to get some track time this fall. Maybe circle back thus winter and buy know good unit, since the rest of the kit and intercooler gear is fabricated.
Just thought the group could share my pain ;)
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User avatar
By worf
#10137
SeanR wrote: Fri Aug 21, 2020 4:32 pm So are they saying that your boost levels never got above 1.8psi? At any RPM?
Blow-off valve?
User avatar
By SeanR
#10145
worf wrote: Fri Aug 21, 2020 4:34 pm
SeanR wrote: Fri Aug 21, 2020 4:32 pm So are they saying that your boost levels never got above 1.8psi? At any RPM?
Blow-off valve?
Was my first thought. On my kit, when I'd get around 4psi I was sucking the intake tube (air side of the compressor) flat and it just killed everything. But that would be more noticeable.

Now, I've heard and seen a couple of kits from a certain vendor who's kits never could make more than 2psi on new SC's and had to be sent back to be fixed. But I've refused to work on them so no clue how things turned out.
User avatar
By worf
#10148
SeanR wrote: Fri Aug 21, 2020 4:42 pm
worf wrote: Fri Aug 21, 2020 4:34 pm
Blow-off valve?
Was my first thought. On my kit, when I'd get around 4psi I was sucking the intake tube (air side of the compressor) flat and it just killed everything. But that would be more noticeable.
Easy enough to check... depending upon where it’s buried.
SeanR wrote: Fri Aug 21, 2020 4:42 pm
Now, I've heard and seen a couple of kits from a certain vendor who's kits never could make more than 2psi on new SC's and had to be sent back to be fixed. But I've refused to work on them so no clue how things turned out.
Well... it ain’t D.R. twinscrews. And it ain’t Murph kits. That leaves... two? My bettin’ money goes on one in particular known for stellar customer service...
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User avatar
By amdavid
#10155
Thanks for sharing, sorry for the pain. It does look impressive! :)

My first thought was blow-off as well, but it's sounding like the latter, punked supercharger.
User avatar
By Crumpler
#10243
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Thanks for following you guys.

Yeah the SC unit is a long story. I bought it as a used Raptor on Fleabay. Arrived with no markings or numbers so big surprise, not a Raptor. I got most of my money back but kept the unit figuring I’d take a shot with it.
I found the manufacturer actually,an old guy out the desert somewhere named Al Martin. Al may, or may not, have been litigated out of production by the Procharger patent attorneys, he’s an interesting dude.
Anyway, The units were called Wynjammer’s, God I never would have put all this out there on RL, lol. They were on kits apparently for GMC trucks early 2000’s.
I rebuilt the SC a few months ago with new bearings and belt. It felt good. Sigh.

So really, no vendors can be blamed for this one.
Just a dude with no real training that wanted to go faster at DE events. All the fabrication was mine.
Actually, Carl sold me his pulley crank without the rest of the kit to his credit.

No blow off valve, assumed with a low pressure set up I didn’t need one. Ironically true now.

They could not find a leak or a tube collapse on the dyno pulls.
Yeah stayed flat at 1.8 at any RPM over 3500 apparently.
I’m going to go get it this weekend and do an autopsy I guess.

Dave H.
User avatar
By TheDeckMan
#10279
Looks damn close to a Vortech V1 internal but using belt vs gears. Use to build cog supercharger setups for VW VR6's back in the day, fun but turbo's came calling. Cool story on the charger origin!
User avatar
By Crumpler
#11840
So you guys the car is back.
Let me ask a few questions :

If the boost maxed out at 1.8 with no difference in rpm curve, then the primary suspect is the SC. More specific, the compression is limited by how fast the impeller spins right? So I can obviously vouch for an increase in pulley speed going into it, so it is a loss of transferred energy by the bearings and belt drive that fail to spin the impeller faster? Meaning junk SC for all intents. I’m not prepared to put more time and energy into this unit.

What does the collective think of the raptor units. This build was such that I could put a Raptor in without a lot of modifications. More time, more money. But I guess I’m a little gun shy hearing about some of these other Raptor kits having trouble generating more then two pounds of boost. Isolated events or general trend?

Dave H.
User avatar
By SeanR
#11889
You may be ahead just to buy a Raptor unit that is sized for your engine and go for it. I've not messed with any of them and had to source a head unit so can't say where the best place is to get one.

I coulda swore you sent me a message about that but I can't find it right now. Sorry man.
Crumpler wrote: Tue Aug 25, 2020 9:00 pm So you guys the car is back.
Let me ask a few questions :

If the boost maxed out at 1.8 with no difference in rpm curve, then the primary suspect is the SC. More specific, the compression is limited by how fast the impeller spins right? So I can obviously vouch for an increase in pulley speed going into it, so it is a loss of transferred energy by the bearings and belt drive that fail to spin the impeller faster? Meaning junk SC for all intents. I’m not prepared to put more time and energy into this unit.

What does the collective think of the raptor units. This build was such that I could put a Raptor in without a lot of modifications. More time, more money. But I guess I’m a little gun shy hearing about some of these other Raptor kits having trouble generating more then two pounds of boost. Isolated events or general trend?

Dave H.
User avatar
By worf
#11892
Crumpler wrote: Tue Aug 25, 2020 9:00 pm If the boost maxed out at 1.8 with no difference in rpm curve, then the primary suspect is the SC. More specific, the compression is limited by how fast the impeller spins right? So I can obviously vouch for an increase in pulley speed going into it, so it is a loss of transferred energy by the bearings and belt drive that fail to spin the impeller faster? Meaning junk SC for all intents. I’m not prepared to put more time and energy into this unit.
With a toothed-belt drive you know that the belt can't be slipping. Energy dissipated to friction (bearings) is just more horsepower sapped from the engine. So, those two things can't account for reduced output pulley speed.

One or more of:
- the crank or SC pulley bearing is slipping on the shaft or pulley (press fit failing if press fit rather than Woodruf key, etc.)
- it can't get enough air into it due to blockage / constriction and/or pumping lose due to a lots of input duct length
- it has maxed it's output potential (seems hard to fathom that 1.8 is its potential.)
- it's leaking
- impeller/coil is worn down/gone missing/broken.

That's "theory" from my end. Never messed with anything other than twinscrews.
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By Crumpler
#11990
Sean, no problem man, I sent that in the middle of the night on the weekend. I used your web site because you were in the middle of the “we fucked up and want you back” saga and phone call from Dr. Bob :)
Anyway, ok got it, I feel better about the purchase if it goes that way.

Dave, thanks, there is a press fitting that I had to repair, I need to look at that.
I dimpled the shaft with a punch and used JB weld, but certainly could have failed.
I will also look at air flow. The inlet is shoehorned for space. I will open it up and see. The pipes, well it’s three inch but I used a barrel intercooler with a 10 inch core. Probably made for the Suburu crowd, I can run it without and see what it looks like. Appreciate the tips.
User avatar
By Shifted
#12006
It sounds like you might still be doing a little troubleshooting of the existing supercharger? Would it be too onerous to disconnect the SC output from your motor input, put a cap on the output with a large pressure relief valve (15 to 20 psi, or a blow off valve with a light enough setting/spring) and a port for measuring pressure? Then, you could run the motor fully NA (with an air filter, I would assume), and monitor the pressure generated by the SC at various RPMs. It won't tell you if it can generate the volume of air needed, but at least you can see if it's making pressure. Alternatively, you could rig up a butterfly valve with some PVC pipe, start with it fully open, then slowly close it and monitor pressure on the pipe between the SC output and the butterfly valve. My turbo easily generates enough volume and pressure to overcome a few 1/4" diameter holes in the charge pipe and the engine running at WOT, so I assume that a SC can achieve the same.


Regardless of what you end up doing, I'm very sorry to hear that you're having trouble with the setup. You clearly put a lot of time and thought into the system. You'll get it sorted out and be very glad that you did!
User avatar
By worf
#12071
Crumpler wrote: Wed Aug 26, 2020 9:48 am
Dave, thanks, there is a press fitting that I had to repair, I need to look at that.
I dimpled the shaft with a punch and used JB weld, but certainly could have failed.
I will also look at air flow. The inlet is shoehorned for space. I will open it up and see. The pipes, well it’s three inch but I used a barrel intercooler with a 10 inch core. Probably made for the Suburu crowd, I can run it without and see what it looks like. Appreciate the tips.
I’m going to back up a step and check assumptions.

Is this *new* behavior? Did it used to make more than 1.8 psi? Did it suddenly stop working? Do we not know if it ever worked? Or are we still in the R&D stage?
User avatar
By Crumpler
#12555
Thank you Shifted, that’s a good idea. I will fabricate something to try and determine boost coming out of the SC, before intercooler and before manifold.

Dave, I have no history on the SC unfortunately. Assume it’s been passed around. The previous owner had never used it “but heard it was working fine” when the owner before him had it. Etc.

The original specs were “up to seven pounds boost”.

I pulled the SC intake off with pics to show intake pipe. Let me know if that seems like a problematic restriction for a V8. It’s very possible that this was an issue, especially at high RPMs.
With that elbow off I can see impeller spinning well and it wants to suck a paper towel into it at idle. Of course, I’m pulling hot air off the engine.
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User avatar
By Crumpler
#13121
Ok, more data now.
In order to try and quantity boost, fabricated a set up with a cap, valve, and spare boost gauge.

Attached it to SC outlet directly. SC still running on crank but engine NA for this experiment.
At idle, and valve open no boost.
At idle with valve feathered closed no boost.
With valve closed. At open throttle, can’t see tach, but est 3000 rpm got three pounds boost.
If this is just pressure at the cap, I’m guessing it would be much less if having to pressure entire manifold.
Which means SC is punked and I don’t have to look farther then this, correct?
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User avatar
By Shifted
#13144
I don't know a lot about superchargers but my understanding is that the boost they produce is a function of the supercharger itself and the motor displacement. So, with effectively no displacement and only 3psi at 3k, I would think that it is not working properly.

But, you may want to get input from someone more familiar with superchargers. And maybe look up data sheets on comparable superchargers to see what they do with low/no displacement on the output side?

Nice work on the test setup! Is your wife shopping for coffin colors? :D
User avatar
By Crumpler
#13171
Shifted wrote: Sat Aug 29, 2020 5:16 pm I don't know a lot about superchargers but my understanding is that the boost they produce is a function of the supercharger itself and the motor displacement. So, with effectively no displacement and only 3psi at 3k, I would think that it is not working properly.

But, you may want to get input from someone more familiar with superchargers. And maybe look up data sheets on comparable superchargers to see what they do with low/no displacement on the output side?

Nice work on the test setup! Is your wife shopping for coffin colors? :D
Hey, thanks for following. And thank you for the ideas.
Yeah, I made the same assumptions. I also didn’t see any linear increases as I goosed the throttle higher. It just seemed to max at 3.
I slogged through a lot of websites and really couldn’t find any comparable data or bench testing. I’m sure it’s there somewhere.
Yes! She’s over it.
There was a comment made recently, 70 percent jest, that if something happens at the track she would prefer the insurance settlement rather then taking care of me for the rest of my life. ;)
User avatar
By Shifted
#13178
No linear increase definitely sounds like it's toast. Sorry :( at least you know for sure now.

Our wives put up with a lot :)
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By worf
#13184
Shifted wrote: Sat Aug 29, 2020 7:36 pm No linear increase definitely sounds like it's toast. Sorry :( at least you know for sure now.
It's a reasonable assumption.

Long story short: @Crumpler if I read your posts correctly, this setup is not known-by-you to have worked before. Or other words, it isn't that it did work well and then all of a sudden stopped working. If that's not correct let me know.

If it is correct, then, unless you want to spend non-trivial time learning a whole lot about centrifugal superchargers, you might as well buy a unit that has some well known engineering behind it. Even better would be one where 928 existence proofs exist that thus give you a comparative baseline.
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By Crumpler
#13281
worf wrote: Sat Aug 29, 2020 8:31 pm
Shifted wrote: Sat Aug 29, 2020 7:36 pm No linear increase definitely sounds like it's toast. Sorry :( at least you know for sure now.
It's a reasonable assumption.

Long story short: @Crumpler if I read your posts correctly, this setup is not known-by-you to have worked before. Or other words, it isn't that it did work well and then all of a sudden stopped working. If that's not correct let me know.

If it is correct, then, unless you want to spend non-trivial time learning a whole lot about centrifugal superchargers, you might as well buy a unit that has some well known engineering behind it. Even better would be one where 928 existence proofs exist that thus give you a comparative baseline.
Amen.
This one’s a boat anchor.
User avatar
By XR4Tim
#13314
Crumpler wrote: Thu Aug 27, 2020 7:21 pm I pulled the SC intake off with pics to show intake pipe. Let me know if that seems like a problematic restriction for a V8. It’s very possible that this was an issue, especially at high RPMs.
With that elbow off I can see impeller spinning well and it wants to suck a paper towel into it at idle. Of course, I’m pulling hot air off the engine.
That elbow should be fine for a V8, however a friend of mine had a similar elbow on a high-powered turbo vehicle, and when it got warm under boost, it would collapse and restrict air flow, cutting boost consistently.

If you did your boost pressure test with the elbow off, it's not your problem and I would condemn the supercharger.
User avatar
By Crumpler
#15725
Procharger P1SC is on its way.

Measurements worked out for the engine bay, new brackets and plate fabrication next.

I assume I will need a real blow off valve for this one.
What is the difference between a BOV and the boost limiter valve that Carl sells?
User avatar
By Shifted
#15814
The boost limiter controls the maximum amount of boost that the supercharger will make. It's similar in effect to a wastegate on a turbo. It may or may not be necessary on your setup, depending on how much boost your supercharger can make vis-a-vis how much you want to run. I can't help much here other than knowing what it does in general.

A blow off valve is designed to release pressure between the supercharger/turbo and the throttle plate after you close the throttle plate (let off of the throttle). If you don't have a way to release that pressure, it will result in compressor surge. I don't know enough about superchargers to know how bad that would be, but I can't imagine it would be good at higher pressures. It's definitely not good for turbo compressors. The other thing that it will do is save you from having components pop off when you let off of the throttle. The MAF and MAF boot being the most likely components to pop off on the 928. Even if they can handle the pressure that you run, once that throttle plate closes, with no place for the air to go, the pressure will build up significantly before it eventually bleeds off.

I can't speak to the boost limiter on your build since I don't know how much pressure you're expecting and I'm not as well educated about superchargers as I am turbos (which isn't much anyway :) ). But I definitely recommend a quality blow off valve. And you really need the "signal" hose for it to be at least 1/4" ID and to be fed from a dedicated 1/4" port from the intake manifold, or from a vacuum manifold. The smaller the hose that you feed the BOV with, the slower it will react to the throttle plate closing. And if it's slow to react, it will defeat the purpose of the having it because it will still allow pressure to build up before it opens.

Personally, I deleted the venturi tube on my 928 and tee'd the BOV signal hose off of the line running between the intake manifold and the power brake booster. It has worked really well for me. I can provide more details on that if it helps.

Instead of a blow off valve, you could get a recirculation valve. It functions the same as a BOV, except that the output gets plumbed into the intake right after the air filter and before the compressor. It makes it a "closed" system and much quieter than a BOV that vents to atmosphere.

One thing that I do know about superchargers and blow off valves is that the blow off valve needs a much lighter spring than when it's used with a turbo. And the blow off valve will probably be slightly open at idle because the supercharger will develop more air/pressure than the motor needs at idle.

Very interested in your build :)
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By Crumpler
#15917
Shifted wrote: Sun Sep 06, 2020 4:31 pm The boost limiter controls the maximum amount of boost that the supercharger will make. It's similar in effect to a wastegate on a turbo. It may or may not be necessary on your setup, depending on how much boost your supercharger can make vis-a-vis how much you want to run. I can't help much here other than knowing what it does in general.

A blow off valve is designed to release pressure between the supercharger/turbo and the throttle plate after you close the throttle plate (let off of the throttle). If you don't have a way to release that pressure, it will result in compressor surge. I don't know enough about superchargers to know how bad that would be, but I can't imagine it would be good at higher pressures. It's definitely not good for turbo compressors. The other thing that it will do is save you from having components pop off when you let off of the throttle. The MAF and MAF boot being the most likely components to pop off on the 928. Even if they can handle the pressure that you run, once that throttle plate closes, with no place for the air to go, the pressure will build up significantly before it eventually bleeds off.

I can't speak to the boost limiter on your build since I don't know how much pressure you're expecting and I'm not as well educated about superchargers as I am turbos (which isn't much anyway :) ). But I definitely recommend a quality blow off valve. And you really need the "signal" hose for it to be at least 1/4" ID and to be fed from a dedicated 1/4" port from the intake manifold, or from a vacuum manifold. The smaller the hose that you feed the BOV with, the slower it will react to the throttle plate closing. And if it's slow to react, it will defeat the purpose of the having it because it will still allow pressure to build up before it opens.

Personally, I deleted the venturi tube on my 928 and tee'd the BOV signal hose off of the line running between the intake manifold and the power brake booster. It has worked really well for me. I can provide more details on that if it helps.

Instead of a blow off valve, you could get a recirculation valve. It functions the same as a BOV, except that the output gets plumbed into the intake right after the air filter and before the compressor. It makes it a "closed" system and much quieter than a BOV that vents to atmosphere.

One thing that I do know about superchargers and blow off valves is that the blow off valve needs a much lighter spring than when it's used with a turbo. And the blow off valve will probably be slightly open at idle because the supercharger will develop more air/pressure than the motor needs at idle.

Very interested in your build :)
Appreciate walking me through this!
New SC is 32 mx boost, 1200 cfm. Made for base HP motors 200-450.
The crank pulley is 6.5 inches, and the SC pulley that is on it is 3.2 inch I think.
I am assuming, and who the hell knows, that this SC will have more output then the 5-7 boost I was looking for.
I had already fabricated brackets for the MAF because even the shitty Wynjammer created enough boost to blow the MAF off coming off throttle.

I would love to see a pic of your BOV set up :smiley:
I almost deleted my venturi already, but then chickened out after reading some threads about maintaining brake booster pressure? But other threads mentioned that most racers have ditched it out of hand.
Regards, Dave.
User avatar
By Shifted
#15983
I'll give you the summary of my understanding of the purpose of the venturi tube on the 928's. I spent a lot of time looking into it and the various vehicles that Porsche did, and did not, put it on.

My understanding is that the purpose of the Venturi tube is to create vacuum when the throttle is open enough that the intake isn't producing vacuum. The reason why Porsche felt it was necessary is because of all of the accessories that depend on vacuum (HVAC and cruise, specifically). They wanted those to continue to function even when the car was cruising at high speed for long periods of time. The brake booster does not rely on the venturi tube generated vacuum. It has a dedicated check valve that holds its vacuum.

However, on a car that has positive pressure on the intake before the throttle plate, the venturi tube does not create a vacuum. The positive pressure is seeking any outlet, including down the leg of the venturi tube that leads to the brake booster. That means that any car with a turbo or supercharger will not create that vacuum when under boost.

To give you an example of how Porsche handled this in a similar era as the 928's: They removed the venturi tube on the 944 turbo. Then, a year or two later, they removed it on the rest of the NA 944's.

I've got a boost/vacuum gauge front and center on my car, so I have gotten a really good feel for when my car is pulling vacuum, neutral, and under boost. It pretty much only pulls vacuum if my foot is off of the throttle, which is expected. It is neutral if I'm giving it very light throttle. And that happens when cruising on flat ground at low speeds. However, there is enough time with the throttle off in those cases that vacuum is being generated much more often than not. At any highway speed cruising, I'm usually at a couple of pounds of boost, even on flat ground.

So, for me and on my car, the venturi tube does absolutely nothing since it can't generate vacuum when it's under pressure.

On a supercharger, I would expect you to see positive pressure even more than on a turbo.

What I did was:

1: Replace both the brake booster and accessory vacuum check valves with new, just to be sure that they were good.
2: Remove the venturi tube itself.
3: Take the line that used to run between the venturi tube and the MAF boot, and connect it directly to the wastegate sensor input. I don't know if the boost limiter you have requires that kind of input. If not, then I would just plug it, or remove it entirely and plug the hole on the boot.
4: Using new large diameter vacuum line (I can get you the specific stuff I used if you want) make a new connection between the brake booster and the intake manifold port.
5: Add a tee in that new line and step it down to 1/4", and run a 1/4" line from that tee to the blow off valve.

This configuration has worked very well for me. If you want to know the specific parts that I used, let me know.

Here is my venturi delete arrangement:
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And here is where I put the blow off valve, circled in red. The closer that you can get it to the throttle plate, the better.
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User avatar
By Crumpler
#16017
Ok, again I am in your service for explaining concepts.
Your set up is clean and fantastic BTW.

My venturi (which is a VW part now that i look at it), connects differently then the S4 apparently. The connection comes off the J pipe, just before the throttle body. The S3 has a hard line up and out of the pipe organ. So the question would be if I use that, it would be after MAF in air flow but before TB. Trying to determine if that would matter.

Cruise and HVAC eliminated in this car anyway, so I plan on venturi delete.
Shopping for BOV with the sensitive springs last night, sounds like the centrifugal SC's benefit from having them, but then got sucked down a rabbit hole by-pass valves v. bov's :)
User avatar
By Shifted
#16037
I'm looking at the parts manual for the 86 LH-Jetronic and it's hard for me to follow where everything connects to without looking into the WSM, so I'm just going to share what I know about my car's venturi pipe.

It has three connections:

1) Goes directly to the intake manifold on the driver's side, toward the front of the car.
2) Goes directly to the brake booster connection.
3) Goes to a port that is after the MAF but before the throttle plate.

The flow from #3 to #1 is what creates the low pressure zone in front of the port for #2, creating a vacuum under the right circumstances.

Eliminating the connection to the pre-throttle plate port is what I did. And then used that port as a signal for the wastegate. If you have no need for a pre-throttle plate signal, you can just plug/cap that.

Be aware that if you eliminate the venturi pipe, it will change how much air can get into the motor at idle. My computer handled that with no issues. I would assume that yours will as well.

From the parts manual for your year, I do see the venturi pipe looks like it has the same general connections, but the one to the brake booster might have a different tee off of it for accessories. Mine has a tee built into the brake booster connection, but otherwise is plumbed the same as yours in general.

The important part is that you need your BOV to be getting its signal from a source that is after the throttle plate. So that it can see both pressure and vacuum. If it's before the throttle plate, it will never see a vacuum.

If your venturi pipe connection is like either of these below, then the logic above applies. Mine is like the lower arrangement with the 7a part.
image.png
User avatar
By Shifted
#16040
BTW - I am using a Tial Q blow off valve. It works really well, but it doesn't have adjustable pressure. You put the right spring in it and that's it. I'm happy with it and would buy it again, but you have to get the right spring with it when you buy it. Otherwise, they are around $20 to $30 per spring to buy them separately.

Whatever BOV you buy, I recommend disassembling it when you get it, inspect it inside and out, verify smooth operation, clean and lube it if appropriate, and then bench test it. Mine was sticking when I first got it and would suddenly pop open at a higher vacuum than it should have instead of a smooth opening at the right vacuum. After cleaning and lubing it, it works really well. Apparently, that's a common issue for BOV's that may have been sitting on a shelf for awhile.
Last edited by Shifted on Mon Sep 07, 2020 2:18 pm, edited 1 time in total.
User avatar
By Shifted
#16043
With respect to BOV versus bypass/recirculation, if this is a race car, I recommend a straight BOV. It will be a little louder, but it will flow more air faster than a bypass or recirculation valve. And the Tial Q that I am using really isn't loud. I can just hear it if the windows are down and I hit it hard. I can hear it more clearly with the windows up. It's not loud either way. Just a new sound for the car.

You will never be at risk of unfiltered air being sucked into the BOV because your supercharger will always be making more air than the motor accepts anytime that the BOV is open. It is always pushing air out of the BOV when idling, never sucking air in.

And a regular BOV saves on plumbing :)

Both ways will work. A lot of it is up to personal preference and intended application.
User avatar
By Crumpler
#16243
Awesome explanations. I appreciate the time.
I pulled my Corky Bell book and crammed a chapter on compressor surge, and I think I have a reasonable plan.
Pics of the Venturi line and origin (spare TB assembly) on the S3 for those following.
Image
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User avatar
By Shifted
#16245
So the solid line shown in the photo in the car is the line coming from the intake manifold that goes to one end of the venturi tube? And the port on the throttle body is where the other end of the venturi tube connects to? With the third/middle/side port on the venturi tube going to the brake booster?
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By Crumpler
#16254
It’s confusing in pic, but hard line connects via boot to that opening under the TB. Second line not pictured runs to air box plenum on drivers side. Line to brake booster is larger black line in pic shaped with 180 bend.
User avatar
By Shifted
#16257
Ok, got it. So, yes. Same method for a venturi delete as my car. The hard line to the throttle body is capped/plugged. The line to the air box plenum is the one that you run directly to the brake booster with a tee in the middle of it for the blow off valve (or recirculation valve, or bypass valve, or whatever you end up using).

I did a very little bit of reading on the boost limiter thing, and apparently it's not "normal" at all. It sounds like what pretty much everyone does is get the right pulley for the supercharger so that max boost is hit at max engine RPM. Some cars are using electronic control of a bypass valve to adjust boost, but that's a pretty advanced approach and not really an aftermarket option. The 928 Motorsports boost limiter seems like it's just an adjustable over pressure release valve. More of a safeguard than a pressure regulator.

Is that how you see it too? What are you finding and what are you planning?
User avatar
By Landseer
#16259
How do you handle the map sensor with the controller? Stock 85 86 unit only reads vac. I thing the boosted guys have stated the need to replace map sensor on that board with a wider range press to vac version.

I know about sensor because I broke diaphragm in one during a vac test. Screwed up all pickup below 3500 rpm.
User avatar
By Shifted
#16265
Isn't the 86.5 a MAF with no MAP? This is all new territory for me but I am anxious to learn what it takes to properly boost the earlier cars.
User avatar
By Landseer
#16266
Dave can answer by looking to see if a vac connector protrudes from the controller at passenger footwell. Am pretty sure it does.
User avatar
By Landseer
#16270
I ended up replacing my controller, as roger had a new Australian one inexpensive, needing only chip swap.

There are a few rennlist threads on map sensor discussion. DaveK9 is fluent on this topic.

Here a snapshots of old controller sitting on desk.
Attachments
Stock MAP sensor, sans little tube to outside port
Stock MAP sensor, sans little tube to outside port
See vac port at bottom right
See vac port at bottom right
User avatar
By Shifted
#16311
Cool. Thank you for educating me. I had no idea that's how the older systems worked. Pretty neat. With a little digging, I found the below diagram. "E" going to the EZK.
image.png
User avatar
By Landseer
#16320
Thanks for the clean diagram. Will corroborate with less clear wsm version. Very timely, am now sorting out vac leak problems on brown car.

And for record, I've told you more than I know about boost. Didn't mean to hijack. Carry on, maybe I can duplicate whatever dr crumpler comes up with some day.

Question to Dave, were you able to use that block you picked up from me in Indiana?
User avatar
By Crumpler
#16647
Good morning gentlemen.
In terms of the what am I planning: trial and error, and luck :grinning:
What's weighing on my mind is the timeframe, next track event is 10-16, so I really got to hustle if this is happening before that, and right now I'm sitting still, waiting for parts.

Yes, stock EZK has the vacuum pick up.
Shifted, you mentioned real time vacuum numbers. I have had a gauge for awhile in the cabin. The 86.5 runs about 20 at idle, and you would really have to stand on the pedal at WOT to hit zero with the NA set up. Is that comparable to your S4 before the turbo?

Speaking of, that superimposed diagram is good but it's from somebody's aftermarket kit right? I think Roger sold it. Cleaner look but I don't think anyone saw better results. I don't remember for certain.

Chris it's good to have you back!
Yea, the engine is still here man. I got a replacement head and cams for it and here it sits, with the rest of my Toft memorial!
It's really nice having it in my back pocket -- just in case I destroy this one at the track, lol.
User avatar
By Landseer
#16687
So you will need to swap the map sensor mounted on the controller board?
User avatar
By worf
#16692
Minor correction: *EZF* has the vacuum connection for load sensing.

EZK does not.
User avatar
By Shifted
#16695
Yes, that diagram is from someone's kit. I don't know whose. For me, it provided a reference to help me see where/how the EZF is getting a vacuum signal.

Unfortunately, I did not have the boost/vacuum gauge installed before the turbo, so I have no idea under what conditions it would hit zero vacuum when it was NA.

Which reminds me, have you bench tested, or tested with a separate known good pressure vacuum gauge, your in car gauge? I found that mine was inaccurate. That's its own story, though :)

Also, I swapped my O2 sensors (one OEM and one wideband) back and forth, left to right, a few times before and after the turbo installation, just to make sure that readings were consistent on both sides and that my sensors agreed with each other.

You can make the October deadline! We have faith in you! Keep the updates coming :)
User avatar
By Crumpler
#16705
Landseer wrote: Wed Sep 09, 2020 11:04 am So you will need to swap the map sensor mounted on the controller board?
Yeah, I wish I knew how important that is. With previous low boost set up I wasn’t concerned. With this one?
worf wrote: Wed Sep 09, 2020 11:18 am Minor correction: *EZF* has the vacuum connection for load sensing.

EZK does not.
Dammit! I made that mistake on RL too.
Shifted wrote: Wed Sep 09, 2020 11:21 am Yes, that diagram is from someone's kit. I don't know whose. For me, it provided a reference to help me see where/how the EZF is getting a vacuum signal.

Unfortunately, I did not have the boost/vacuum gauge installed before the turbo, so I have no idea under what conditions it would hit zero vacuum when it was NA.

Which reminds me, have you bench tested, or tested with a separate known good pressure vacuum gauge, your in car gauge? I found that mine was inaccurate. That's its own story, though :)

Also, I swapped my O2 sensors (one OEM and one wideband) back and forth, left to right, a few times before and after the turbo installation, just to make sure that readings were consistent on both sides and that my sensors agreed with each other.

You can make the October deadline! We have faith in you! Keep the updates coming :)
Ok, I will take it up a notch!
Either I need more pedal by October or need to drive better!
Yeah the gauge is right, long story as well ;)
User avatar
By Landseer
#16713
Contact dave k9 and ask. Or john speakes.

I can tell you that with vac disconnected the car is an abject slug. Could be very important. Modification of map sensor is a very basic core thing in turbo boosting all kinds of cars, so search that.

Hate for you to lose performance that you are striving to add in the first place
User avatar
By Shifted
#16841
Are you taking any kind of before and after performance measurements?
User avatar
By Crumpler
#16878
Landseer wrote: Wed Sep 09, 2020 12:33 pm Contact dave k9 and ask. Or john speakes.

I can tell you that with vac disconnected the car is an abject slug. Could be very important. Modification of map sensor is a very basic core thing in turbo boosting all kinds of cars, so search that.

Hate for you to lose performance that you are striving to add in the first place
True enough. I will do some home work on that. I also sent Dave a PM on the other channel.
Shifted wrote: Wed Sep 09, 2020 7:15 pm Are you taking any kind of before and after performance measurements?
I have dynojet runs from several years ago NA. I believe with the Porken chips I was around 300 rwhp and like 290 torque.
My initial goal was to get a modest 60-80 hp with a low boost SC. Just something to be, I won’t say competitive because it’s DE, but maybe relevant.
It’s such a god damn arms race at these events. Maybe it always was and I’m just late to the party.
I have the car down to 2900 lbs., so it is what it is.
User avatar
By Shifted
#16963
Those seem like great numbers!

I once heard, and mostly agree, that performance is 90% operator and 10% equipment. But, I think that only applies when your equipment is in the same general class.

The general rule of thumb is that you double your horsepower for every atmosphere (14.7 psi) of boost. 90 hp is 30% of your NA 300hp. 30% of 14.7 psi is 4.41 psi. Really general guideline and many variables can significantly affect the outcome. But, for my car, that guideline turned out to be a close guess for my power increase.

Have you done any calculations on how much pressure your supercharger is going to produce? Because from what I'm seeing, it's going to be way over 10psi. At 6,200 rpm, you'll be spinning the supercharger at around 50k rpm with the 3.2" pulley. With our 5L motor, I would be expecting it to give you somewhere in the ballpark of 15 to 20 psi. Definitely well over 10psi. Does that jive with your own math and expectations? Maybe I'm missing something in my math :)
User avatar
By Shifted
#16964
Found this chart that shows your supercharger:
image.png

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