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Full boost only in high RPM range

fri3dchick3n

fri3dchick3n

New member
Hey, Ive been noticing that I usually get only full boost in my higher RPM range while WOT. It'll be short a few blocks and work its way up in the end of each gear.

Ive tried moving my BBV back to its original position and it made my boost a little worse. So I set it back, to the BBV mod. Not all the way though.
Ive checked for vacuum leaks and replaced a lot of my vacuum lines over the year, so they are all good.

About 2 months ago, my Idler pulley was making a lot of noise and actually ended up shredding off and the belt of course fell off too, the belt was in good condition still so I reused it after I installed my new pulley. Could the problem be the belt?

I have a scheduled tune on the 21st and would like to figure this out before the tuning date.

Is there suggestions that can point me in the right direction to find this problem.

Thanks.
 


Has this gradually started or been happening since you installed headers?

5 PSI at 4000 RPM then creeping up to 7 by the top of a gear is pretty normal for a stock pulley car.

Get a real boost guage.
 
Its started before the header install.

So far I do have the stock pulley on the car, but I remember before, If I went WOT, I would see full boost most of the time.

I want to get myself the boost deal for the aeroforce. Its around $60 though. : \
 
a little sunpro or equus boost guage would be less expensive.

Does the boost pattern follow the weather?

Because thats another huge factor in boost levels.

Namely the temperature of the air going into the blower. Higher the temp, less dense the air, less boost.

And the inverse is also applicable.
 
At night its a lot cooler. The car runs a little better at night here but the boost is the same.

I think im gapped at .055, can spark plugs affect this at all?

I will look into those boost gauges.
 


Hrmm, Not sure. Didnt get a chance to drive my car much this winter. I was in Kodiak for 2 1/2 months fishing for pacific cod. But when I did drive it.. It was driving good : \

I do watch my KR as well and theres no pattern with the boost.
 
Not sure what you are complaining about. Roots style blowers are suppose to hit peak boost numbers "instantaneously" and I say that cautiously, but there are other factors such as the tune, rpm, throttle position, etc. that play into how much the car will allow a certain amount of boost at any given time. Also, remember this: boost is just a pressure reading inside the engine which technically is a measurement of the inefficiency of the engine's ability to move air in and out of it. The higher the rpm, the more amount of air the engine is trying to move through it, hence without the correct "breathing" mods the more pressure you are going be building up in the engine. In layman terms, higher rpm at WOT, more pressure, higher boost number.
 
Roots blowers typically fall off at high engine speed in more ideal applications like LSx situations.

Thats how much our engines suck at high speed cylinder filling.
 
So what I'm experiencing might just be normal? Even if it started doing this a little bit ago. How's everyone else's boost at wot. Stock pulley or even smaller pulley.
 
i had the same thing happen to my car it had a lot of miles like 220 and it was only gettin like 8 psi with a 3.4 pulley and headers replaced the blower with a lower mileage used one and ported and polished it and i see 11 to 12 all day long in the hot and sometimes 13 when its winter the old blower had all the rotors pealing but im not sure thats what caused it it just didnt like to boost anymore
 


00grandprixgtp said:
i had the same thing happen to my car it had a lot of miles like 220 and it was only gettin like 8 psi with a 3.4 pulley and headers replaced the blower with a lower mileage used one and ported and polished it and i see 11 to 12 all day long in the hot and sometimes 13 when its winter the old blower had all the rotors pealing but im not sure thats what caused it it just didnt like to boost anymore
Click to expand...

I agree, its amazing what a P&P can do for boost levels, i was seeing 4-5 bone stock, then 6-7(maybe 8 at shift) with my 3.4 setup, after just porting the bottom of my blower and polishing bottom and cleaning the hell out of it, im seeing 10-12 all day and thats at 85-90* weather
 
Whoa... you want to get a boost deal for the aeroforce? Why not just look at the map reading and be done?

Cracked up when I read that your car was a few lego blocks short of full boost..
 
fisher580 said:
I agree, its amazing what a P&P can do for boost levels, i was seeing 4-5 bone stock, then 6-7(maybe 8 at shift) with my 3.4 setup, after just porting the bottom of my blower and polishing bottom and cleaning the hell out of it, im seeing 10-12 all day and thats at 85-90* weather
Click to expand...

a ported blower should net lower boost levels, not higher.
 
BillBoost37 said:
Whoa... you want to get a boost deal for the aeroforce? Why not just look at the map reading and be done?

Cracked up when I read that your car was a few lego blocks short of full boost..
Click to expand...

So what map reading should I be looking for, what numbers should I be seeing?

I dont know how to use my aeroforce fully yet to really take advantage of it.

I do have the outlet ported out on my blower.. As Bio mentioned, It'll lower boost levels.. Maybe its just my port causing this?
 
Or change in air density etc.

Look up MAP or Boost in your aeroforce. You don't need any additional modules.. the info is right at your fingers.
 


You were right! This Aeroforce is getting better and better :]

Well I monitored my boost.

At wot it will be around 6.5 and going to to 9 psi in the higher rpms in first gear. Other gears 6.5-8 PSI.

So this is Im guessing sounds normal.

Oh, and my stock boost gauge was acting pretty good this time. Very weird. Who cares, its working good now lol.
 
fri3dchick3n said:
You were right!
Click to expand...

I knew it had it in there, because I've used it when I've had a need to see what boost was on a crapbox GP. Regal has a digital readout in the cluster (actual numbers), Bonneville had a true gauge in the cluster (stock yes). It's only the supposed sportcar that got the silly block game gauge.
 
BillBoost37 said:
I knew it had it in there, because I've used it when I've had a need to see what boost was on a crapbox GP. Regal has a digital readout in the cluster (actual numbers), Bonneville had a true gauge in the cluster (stock yes). It's only the supposed sportcar that got the silly block game gauge.
Click to expand...

Wow, a gauge or the digital readout would have been pretty awesome. Eh, at least we get to stack legos all day :)
 
fri3dchick3n said:
Hey, Ive been noticing that I usually get only full boost in my higher RPM range while WOT. It'll be short a few blocks and work its way up in the end of each gear.

Ive tried moving my BBV back to its original position and it made my boost a little worse. So I set it back, to the BBV mod. Not all the way though.
Ive checked for vacuum leaks and replaced a lot of my vacuum lines over the year, so they are all good.

About 2 months ago, my Idler pulley was making a lot of noise and actually ended up shredding off and the belt of course fell off too, the belt was in good condition still so I reused it after I installed my new pulley. Could the problem be the belt?

I have a scheduled tune on the 21st and would like to figure this out before the tuning date.

Is there suggestions that can point me in the right direction to find this problem.

Thanks.
Click to expand...


what is this bbv mod you speak of?
 
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