Engine/Transmission (1998.5 - 2002) What is normal boost levels?

[Roadhogz]

I installed my boost gauge today (ispro) and need to know what's normal for a 98. 5 24v auto with a cat back 4" K&N air filter and a VA module with no boost fooler?



Did a test run and at full throttle acceleration I get about 19-20psi. Cruising at 70 mph 9-10 psi and at 60 mph 5-6 psi. No wind. Thanks.

 

[mongoose]

on my 99, i have a K&N only. I usually see about 17-18 at max. cruising, depending on the grade of the road, usually anywhere from 3-10. Hope this helps.

 

[BarryG]

Roadhogz:

I believe that 19-20 is about max for stock without a boost fooler of some sort and disabling the wastegate by one of the various methods. I think you said you have a va box and that will yield more boost with the addition of a boost fooler and wastegate mod. My ez(more or less the same as va except has a boost fooler built in) will do 28psi max with the wastegate modified.

 

[Roadhogz]

How do I modify the wastegate.

 

[Hohn]

Originally posted by Roadhogz

How do I modify the wastegate.

Road, it depends on what turbo you have. If you have a 2001-2002 automatic, you have the small turbo and the hardline wastegate. That means you will have to rig up a turnbuckle or j-hook to get more boost. Search on "turnbuckle" and you will get good info.



If you any other 24V, you have a larger turbo with a brass elbow that can be modified to allow more boost. This fitting is in an an air circuit that tells the wastegate how much boost there is. If this fitting is more restrictive (or there is a small hole in it), the the wastegate will "think" there is less boost than there is.



This is the mechanical portion of getting more boost. There is an electrical aspect as well. You need to have a "boost fooler" of some sort which hides the real boost from the MAP sensor. The MAP only sees 20 PSI, even when you have more.



Most newer boxes have BOTH items on them (they come with the brass fitting, and have the electronic boost fooler built in)



HOHN

 

[Roadhogz]

I bought a BD boost fooler to go with my older VA box. It also came with a brass elbow. The brass elbow that came with the kit was way more restrictive. I installed the kit with the supplied elbow and lost power so I took the fooler kit off. Then yesterday I tryied the fooler again, but WITHOUT THE SUPPLIED ELBOW and ran my stock elbow. My power was back and I think it accelerated a little better, but sill only showed 19-20 psi max.



So, my question now is, if the map sensor thinks there is only 20 psi with a boost fooler, will it show only 20 psi on my boost gauge? Thanks.

 

[Hohn]

Originally posted by Roadhogz

I bought a BD boost fooler to go with my older VA box. It also came with a brass elbow. The brass elbow that came with the kit was way more restrictive. I installed the kit with the supplied elbow and lost power so I took the fooler kit off. Then yesterday I tryied the fooler again, but WITHOUT THE SUPPLIED ELBOW and ran my stock elbow. My power was back and I think it accelerated a little better, but sill only showed 19-20 psi max.



So, my question now is, if the map sensor thinks there is only 20 psi with a boost fooler, will it show only 20 psi on my boost gauge? Thanks.

NO! Your Boost gauge measure boost directly, not through the MAP sensor. The MAP sensor tells the ECM how much boost there is so it knows how much fuel to inject and when. Basically, the boost fooler allows a higher boost pressure at max fueling (since the ECM gives max fueling, but limits boost). By allowing more boost for a given amount of fuel, you have lower EGTs.



The only way you would ran higher EGT running more boost is if you ran boost high enough to hit the choke point of the turbine housing, which can happen with the small HY. There is no way you should have lost power by running more boost. Similarly, there's no way you should have gained power by running less.



POWER is a function of fueling level ONLY-- how much boost you have doesn't matter. The amount of boost you have only determines where your EGTs will fall from cold to hot.



You should put on your boost fooler fitting and then figure out why you don't have the power you need. It's not reasonably possible to lose power from running more boost (within the turbo's map)



HOHN

 

[Roadhogz]

The only time I lose power is when I install the fooler and the eblow that came with the fooler kit ( the restrictive elbow). The power came back when I installed the fooler and the stock elbow ( less restrictive elbow). My boost is the same with or without the fooler, is that possible?



I'm assuming I need more fuel to make more boost???