: Increase boost on stock pulley?



HUGN*RDS
03-04-13, 12:44 PM
I'm not sure if this has been covered, I did a search but came up empty-handed.

My question relates to the stock boost levels. From what I can see most people get about 8-9psi when they have a stock setup. Considering the supercharger spins faster and faster with RPM since it is driven by the crank pulley, how come the boost levels reach 9psi at < 5000rpm but it doesn't go any higher especially when I shift at 6500rpm?

From my experience with Eaton roots superchargers this has to do with the boost bypass valve and it creates an alternative path for fresh air to reach the intake manifold and avoid the supercharger. Without knowing much about this bypass valve I wouldn't know if I could easily modify it or something. On my previous car, simply removing a vac hose from one of the supercharger's bypass valve's nipples, and plugging that vac hose with a screw or something, would hold shut the bypass valve longer and result in higher boost. I was able to get about 20whp on my old car from just this simple mod. The HP increase was strictly from 6500-7000rpm because that is where the bypass valve would typically operate.

One advantage of having a pulley combination that increases boost beyond stock is the immediate increase in torque, because that psi level is reached earlier in the rpm and throttle ranges. However, our stock setup in the LSA seems to be sufficient to produce some more boost as far as I can tell. Has anyone taken the stock pulley > 9psi?

Only mod is a D3 intake. I was thinking of getting HPtuners or something, too, if anyone has some recommendations for user-friendly tuning software. Thanks fellas.

Moparman4444
03-04-13, 05:01 PM
What your suggesting is tweeking the blowoff valve which will result in boost spikes over 9psi. I don't know if it can be done safely because the valve is doing what it was designed for. I would like to hear from some mechanics on this point as well.

qictrk
03-05-13, 01:43 AM
I think if it were that easy, most everyone that wants to mod, would have done that by now. Maybe you might pick up another 1/2lb on a stock pulley. But to feel a real
change from the seat of your pants and the dyno, your going to have to change the pulley like me and many others on this forum. I messed with the blowoff, but didn't see any
real changes in power. Cecil................

6speeder
03-05-13, 08:51 AM
I don't believe that bypass valve opens WHEN YOU ARE UNDER BOOST until about 12 pounds. It's not holding your boost down to 9 pounds, that is what the blower is producing with a stock pulley.

HUGN*RDS
03-05-13, 09:07 AM
I don't believe that bypass valve opens WHEN YOU ARE UNDER BOOST until about 12 pounds. It's not holding your boost down to 9 pounds, that is what the blower is producing with a stock pulley.
I agree that the valve does not open until a certain boost is reached (I think there is a 1-2psi difference in the manifold from the supercharger due to the aftercooler). If it didn't, there would be boost spikes, and that is where I am trying to get to understanding in this thread. Would it be unreasonable for me to expect a 1-2psi increase when I diable the bypass valve?

Does anybody have a RPM/PSI chart for the stock 1900? Shouldn't it boost more than stock if it is spun faster?

Low_ET
03-05-13, 09:29 AM
Does anybody have a RPM/PSI chart for the stock 1900? Shouldn't it boost more than stock if it is spun faster?

Search the forums for "P-Valve". This has been discussed before.

Eaton Publishes the supercharger data.
General Info:
http://www.eaton.com/Eaton/ProductsServices/Automotive/AutomotiveAftermarket/Superchargers/PCT_221787
Boost-RPM map:
http://www.eaton.com/ecm/groups/public/@pub/@eaton/@per/documents/content/ct_127899.gif

HUGN*RDS
03-05-13, 09:31 AM
here is the graph

qictrk
03-05-13, 10:24 PM
Joe, I've had a few dyno runs and some were with the P valve stock and some with it open. The gains were very small, maybe 5 rwhp as I remember. Maybe I'll start digging through
my papers and see if I can't find them. If it were more than 5, I'll post it here. Cecil..............

wait4me
03-06-13, 10:09 AM
The only time you would see a gain on the p valve mod is if the boost is either
A: higher than the selected boost level from the factory via the computer.
B: The boost valve is not pushing the valve shut with the set screw and adjuster bolts. " the spring inside the boost valve should be pressing hard against it being shut so it can snap shut faster when no Vac on V valve is seen.
C: The hard limit is hit inside the valve itself as seen on the P port to override itself.


When adjusting the valve, you can make horsepower faster by clocking the valve to put more spring tension on it. It will still work properly and open itself to relieve boost when normal driving, but when you floor it, it will slam itself open faster allowing for a faster boost climb. When set at the factory, it isn't as much spring loaded against itself so it opens slower.

Here is a video also of how it can over ride itself.

http://www.youtube.com/watch?v=Vz8ljMabPTI


Also to check for proper max boost, check the valve itself to make sure it is fully shut all the way when the key is off. If it is shut, you have full ability for max boost. Then the rest is the other stuff.

I usually suggest pulling the P port for the reason of if I want boost, I get it any time. The Vehicle will still work properly and will still turn off the boost when light and regular driving.


Another secret for Faster boost entry is to instead of using the V port at the SNOUT, move it over to the P port on the supercharger itself, "im not talking about p valve on the bypass valve" And this will make it super fast on getting into boost.

There is still vac on that lid port while light and normal driving, but it will shut the valve easier and quicker once you get it into the throttle.
Then it will go shut faster as well during a decell. It will help with cooling of the charge quicker as well as it is getting out of boost faster.

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Also in that graph for horsepower you posted, it could have been seeing a misfire or a lot of KR during that run and it started to pulse the bypass valve so it showed a gain on the other way.. That, or they where hitting the mechanical safety for added boost.

baabootoo
03-06-13, 10:49 AM
Wow, great video for us visual people!

Stillborn
03-06-13, 02:32 PM
jess, can you do a vid of how to pull and cap the lines for those that are bucking/surging at 12 psi with upper and or lower pulleys? as you stated this problem never happened in summer weather when i got tuned but once winter came it has reared it's ugly head.

austin
03-07-13, 07:16 AM
I would like to see a before / after dyno chart done on a "Completely Stock Motor" with only the boost valve bypassed for the next run.

The dyno sheet should display HP/TRQ with the boost chart vs rpm at the bottom. Again, NO mods, NO pulley, a completely stock engine.

Can someone possibly run this test for us and post the results for all to see. Thanks. :)

wait4me
03-07-13, 10:20 AM
I have run that test as you are asking for Austin, It made no change on a STOCK car, unless the car was getting kr for bad gas.

The gains from this are only after you start adding in more boost over stock settings.

austin
03-07-13, 10:36 AM
I have run that test as you are asking for Austin, It made no change on a STOCK car, unless the car was getting kr for bad gas.

The gains from this are only after you start adding in more boost over stock settings.

Thank you.. :)

HUGN*RDS
03-07-13, 02:00 PM
I don't believe that bypass valve opens WHEN YOU ARE UNDER BOOST until about 12 pounds. It's not holding your boost down to 9 pounds, that is what the blower is producing with a stock pulley.

I think it opens at 9 because I have never seen my stock gauge go above the ~9psi mark. If it opened at 12 pounds, I would guess the gauge would indicate this. but we need to account for the loss due to the intercooler.


I have run that test as you are asking for Austin, It made no change on a STOCK car, unless the car was getting kr for bad gas.

The gains from this are only after you start adding in more boost over stock settings.

Me too, see dyno graph. Stock engine and pulley saturn redline with a similar roots setup/bypass valve, intercooler configuration. theoretically they work the same way, that's the point of my thread, right? The only difference between the two back to back dyno runs was that I modified the boost bypasss valve so it stayed closed the entire dyno run, which resulted in more boost being made, or technically now the boost wasn't being limited. think of the bypass valve as a wastegate. I disabled the wastegate. To mention, like your video pretty much, the same concept we can do using this bypass valve.The rinky dinky saturn redline made 15whp more. Now triple the displacement in our V8's and couldn't the same or better gain be made?

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Thank you.. :)

see my above post and dont believe everything you read on the internet.

wait4me
03-07-13, 02:39 PM
I think it opens at 9 because I have never seen my stock gauge go above the ~9psi mark. If it opened at 12 pounds, I would guess the gauge would indicate this. but we need to account for the loss due to the intercooler.



Me too, see dyno graph. Stock engine and pulley saturn redline with a similar roots setup/bypass valve, intercooler configuration. theoretically they work the same way, that's the point of my thread, right? The only difference between the two back to back dyno runs was that I modified the boost bypasss valve so it stayed closed the entire dyno run, which resulted in more boost being made, or technically now the boost wasn't being limited. think of the bypass valve as a wastegate. I disabled the wastegate. To mention, like your video pretty much, the same concept we can do using this bypass valve.The rinky dinky saturn redline made 15whp more. Now triple the displacement in our V8's and couldn't the same or better gain be made?

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see my above post and dont believe everything you read on the internet.



The boost valve at wide open throttle is shut on your stock car. You are talking about 2 different setups here. On the V is totally different. The blowers are totally different.

This isn't a redline... This is a V8 V with a Different software set, different parts, different blower, different displacement, different well EVERYTHING. Even the limits in the ecm are different.

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Another thing, like I said before, that car in your dyno graph was getting kr, probably due to the customer running 87 octane in his car when it should have been 93, so as a safety it pulled some timing on the high end. I have seen that a lot on those smaller engine cars.. Everyone thinks they can run 87 in everything even though it is supposed to have 91up to make full power.

Chrispy
03-08-13, 01:52 PM
Another cheap/easy way to pick up ~1.0 pds of boost is with a better induction setup. My stock setup would peak at 9#s, with the Airaid and K&N 1044 I'm seeing over 10#s.

(I'm running 11.85 @ 120.3mph with drag radials and Airaid with K&N as only mods in my 6spd manual wagon)

Cheers,
Chris

Stillborn
03-08-13, 05:58 PM
can someone post a video of how to pull and cap the boost valve for those having it close at 12psi? thanks in advance.

Ste_V_e
03-09-13, 03:38 AM
can someone post a video of how to pull and cap the boost valve for those having it close at 12psi? thanks in advance.

Would you have to do the boost bypass mod when running only a 2.5 metco pulley?

Stillborn
03-10-13, 02:22 PM
Would you have to do the boost bypass mod when running only a 2.5 metco pulley?

yes, in the summer it wasn't an issue, once winter temps (denser air, lower iat's) came, it will dump boost over 12psi.

Da V-Man
03-10-13, 05:48 PM
Would you have to do the boost bypass mod when running only a 2.5 metco pulley?
Since you have a pulley, you have a tune. Have your tuner up the allowed boost in the tune and leave the bypass hardware alone.

HUGN*RDS
03-15-13, 09:51 AM
hey guys, I've been intending to reply earlier but my account went into restricted mode for no reason. it just got unlocked today, weird..


The boost valve at wide open throttle is shut on your stock car. You are talking about 2 different setups here. On the V is totally different. The blowers are totally different.

This isn't a redline... This is a V8 V with a Different software set, different parts, different blower, different displacement, different well EVERYTHING. Even the limits in the ecm are different.

----------

Another thing, like I said before, that car in your dyno graph was getting kr, probably due to the customer running 87 octane in his car when it should have been 93, so as a safety it pulled some timing on the high end. I have seen that a lot on those smaller engine cars.. Everyone thinks they can run 87 in everything even though it is supposed to have 91up to make full power.

First that was my car's dyno and I always ran 93 octane or better in it. Always. Also on that day the dyno recorded higher maximum boost pressure above the stock boost pressure. This is a very well documented modification for that car and I've seen it with my own very eyes..They have different parts and software, yes nothing there is the same, however the induction setup is almost identical because it goes: intake, TB, blower inlet, blower rotors/bypass valve, aftercooler (intake manifold), head. I described both cars in once sentence. It points me right to the quote below, of which I have the exact same experience, interceptor gauge reading >10psi at WOT with my D3 intake..

I bet you won't disagree that they're similar after you watch this animation video of s/c intake air:
http://www.youtube.com/watch?v=14MaYSMPc1c&feature=youtu.be


Another cheap/easy way to pick up ~1.0 pds of boost is with a better induction setup. My stock setup would peak at 9#s, with the Airaid and K&N 1044 I'm seeing over 10#s.

(I'm running 11.85 @ 120.3mph with drag radials and Airaid with K&N as only mods in my 6spd manual wagon)

Cheers,
Chris

I am seeing boost spikes above 10psi as a result of my intake too. I am curious to see if it could go up a little more with some tweaking. Seems the car isn't bleeding off the charge pressure after 9psi.