Pump Gas Limitations

[Chris@Rvengeperformance]

I know this is a sensitive topic for some, but I'd like to get a discussion going. There are many that say pump gas is a waste of time. Well, I for one like to be able to run times at the track that fully represent my "street" mode that the car sees daily.

If that is not your cup of tea I am not here to argue with you.

The point of this thread is to talk about the reasons why we are stuck at much lower boost levels than other platforms on pump and what can be done about it. What about our engine or cylinder head design is lacking that causes us to have to run so much less boost than say an Evo? Many say that cleaned up combustion chambers like DR or other heads help, but there has really been not much evidence posted to support that.

I know our stock timing map may be too aggressive for high boost, but then we hear from many that running high boost and low timing doesn't work either. I also know that the whole real point is airflow, but it is easy for most of us to get on the same page if we talk about boost.

Basically the threshold for knock on typical 93 octane gas seems to be as low as 15 PSI for some and maybe low 20s for others. Most people do not seem to venture much about 15 lbs, but that really holds us back.

If you don't want to talk about boost then you can think of it in terms of power. Most cars seem to do well to get to 400-450AWHP with bolt on style turbos and pump gas. What can we do to get past this?

Let's pretend these 3 options are off the table at the moment:

1)Methanol/water injection
2)Race Gas
3)E85

What can we do then?

[Greg E]

My theory has been this is a result of high EGTs from a poor/very restrictive exhaust manifold, very mild cam overlap and shitty innercoolers.

[Greg E]

About high timing, that's bull... Peak load, the timing dips all the way back to 10-12degrees and even as low as the single digits if you get enough airflow on a stock timing map. You run a piggy back, then suddenly you run into too high of timing.

[Chris@Rvengeperformance]

My theory has been this is a result of high EGTs from a poor/very restrictive exhaust manifold, very mild cam overlap and shitty innercoolers.

As far as inter-cooling goes you never see any real results posted about that. Even with a FMIC the ceiling seems to be really low.

Even the all out built to the wall cars never seem to run much past low 20s.

[Greg E]

Many say that cleaned up combustion chambers like DR or other heads help, but there has really been not much evidence posted to support that.

Missed this note:

I have first hand experience with DR heads. Every car running them were able to run MUCH more boost on pump. Both my previous 95 Stealths were able to run as much as 17-19psi on pump with little to no knock. They performed extremely well!

[NickS VR4]

My theory has been this is a result of high EGTs from a poor/very restrictive exhaust manifold, very mild cam overlap and shitty innercoolers.

Don't have much to add, but I wonder if Gil's manifolds will help with this.

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[Chris@Rvengeperformance]

Missed this note:

I have first hand experience with DR heads. Every car running them were able to run MUCH more boost on pump. Both my previous 95 Stealths were able to run as much as 17-19psi on pump with little to no knock. They performed extremely well!

good to know and have some solid data. Sounds like they are worth 2-3 more PSI.

[Greg E]

As far as inter-cooling goes you never see any real results posted about that. Even with a FMIC the ceiling seems to be really low.

Even the all out built to the wall cars never seem to run much past low 20s.

That's pretty good actually.

[Chris@Rvengeperformance]

Don't have much to add, but I wonder if Gil's manifolds will help with this.

Sent from my Galaxy Nexus using Tapatalk 2

I am looking forward to the dyno testing that has been proposed on them. I'd certainly pick one up if it were worth some tangible gains.

[Greg E]

Don't have much to add, but I wonder if Gil's manifolds will help with this.

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Debating dropping the coin for one. He needs to make a rear one too!