Contour Enthusiasts Group Archives Forums General Dyno and Drag New 2.5L Turbo Benchmark thanks to Chris!

Originally posted by Tim:

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Hey now.. I thought you said you were going to shoehorn that big old' LS v8 of yours into a GL first ?

With all of these camaro-eating Contours out there now, we could stand to have one or two V8 grocery getters...

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I did say that, didn't I?
Notice the "slight modifications" phrase.

Originally posted by warmonger:

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I know he isn't using secondaries so why the drop in torque at the place where the secondaries normally open up?
I thought with full controll over the timing it would enhance that portion of the graph?

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Originally posted by DemonSVT:

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Originally posted by warmonger:

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I know he isn't using secondaries so why the drop in torque at the place where the secondaries normally open up?
I thought with full controll over the timing it would enhance that portion of the graph?

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But he is using the secondaries.

I keep telling him to pin them and set the IMRC point to 2000rpm or lower to remove the harsh jump and pressure loss from them opening and see what kind of graph it makes.
IMO it would generate boost sooner and it would definitely get rid of the drop in mid range power.

Boost pressure is a measurement of restriction. It is a major restriction running on only the primary ports then followed by a big pressure drop opening the even larger secondary ports.

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Yes, that intake with the fancy secondaries is made for NA. There is meant to be a negative pressure in those runners for them to work optimally (relative to the outside air).

Ideally, a metal single-runner 3L upper would be best, with the 2.5L LIM matched and siamesed, and the heads tapered match on the ports. Leave the injectors pointed at the primary ports. The gas is going to get in there, no matter what

That could take you over the 400WHP mark.

Just my opinion.

Originally posted by Chris Hightower:

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Ideally, a metal single-runner 3L upper would be best, with the 2.5L LIM matched and siamesed, and the heads tapered match on the ports.

That could take you over the 400WHP mark.

Just my opinion.

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Not necessarily.

The split port manifolds have a much high cfm flow ability and a much larger port area. That is a given.

With forced induction the less restriction the more power from the exact same setup. Advantage split port manifolds.

Since Chris is already at or just over the compressor's rated limit and doing it with less boost pressure I'd say his setup in very efficient. (I calculated 110-112% efficiency vs norm)
Switching to smaller intake ports might get him to see higher boost pressure (it's just a resistance measurement) but definitely will produce lower overall cfm flow and therefore less power.


Now the ST220 did come with an Aluminum oval port manifold that is supposedly hand portable. (i.e. no bends and you can accurately open up each port identical to the other)
If have not seen one of them personally nor could fathom a price estimate.
It does sound like an intriguing part though...



Now the larger plenum volume of the oval UIM can show benefits over a stock split port manifold on a NA engine. (3L especially)
However most people seem to forget EHing the split port UIM adds volume as well as max cfm flow ability. The latter of which it already has an advantage in.

For instance I gained roughly 18-19% port volume over my DH UIM. That is at or "more likely" just slightly beyond the limit of the split port UIM though.

Funny thing is the 3L is 16.5-18.2% (vs 2544/2499) larger in displacement. Who knew...