Contour Enthusiasts Group Archives Forums General Dyno and Drag EH'd UIM dynoed with confusing results.

Originally posted by zm830101:

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you guys mention an intake obstruction, but what about exhaust? A stock y pipe would definetly limit hi rpm breathing

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What is being referred to is changes that were made between the two dyno runs. The exhaust has remained unchanged between runs so, even if it were a restriction, it shouldn't reduce the readings, only reduce the gain or if it were at it's flow limit there could be no gain.

If you look at Ronan's signature you'll see that he has a high-flow exhaust already installed, MSDS headers, P&P'd heads, etc., so the exhaust shouldn't be a limiting factor.

The EGR mod doesn't "restrict" the intake, it blocks off exhaust gases being recirculated into the intake. The reason this creates a problem is that the ECU is expecting to see a certain % of exhaust gas coming into the intake stream. When the computer fails to get that reading it won't advance the timing because under normal conditions, this would lead to spark knock and drastically shorten the engines life .

As has been stated earlier there haven't been any demonstrated benefits to doing this modification and there can be problems created by doing it, so the conventional wisdom is to avoid it.

Certainly, one can't get valid dyno numbers if this mod has been done and something else was also changed (UIM in this case). I suspect/hope that the UIM actually made some gains for Ronan and the EGR Mod wiped them out.

Regards, Alan

Quote:

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I've dyno'd my car with and without an SVT uppper intake, and in both cases I got power plummeting after 6000 rpms.

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I was referring specifically to this post. my fault. he mentions exhaust & mystery mod but if he is still using an unmodded y it would more than likely be the source of restriction and cause the choking of power from 6000 up

Originally posted by zm830101:

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Quote:

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I've dyno'd my car with and without an SVT uppper intake, and in both cases I got power plummeting after 6000 rpms.

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I was referring specifically to this post. my fault. he mentions exhaust & mystery mod but if he is still using an unmodded y it would more than likely be the source of restriction and cause the choking of power from 6000 up

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I missed that too, but I still think it's not likely the Y-Pipe. I don't know that it's not, just think it's not.

I know that when I dyno'd my Mystique (KKM, SVT TB) it ran strong right to the rev limiter (I'll try to find the time to pull the graph).

The exhaust Ronan has should help not hinder and there is plenty of reason to believe the "mystery mod" blocking the EGR would cause the problem as it likely is not allowing the timing to advance.

The stock Y-pipe is definitely a restriction, but the cars still run strong right to the limit just not as strong as they could.

Regards, Alan

Originally posted by Ronan:

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...should I even expect this modded UIM to outperform the 98 SVT UIM?
Are the plenums actually enlarged during the EH process, or merely smoothened out? If they are not enlarged, then would a factory SVT UIM still outperform a modded standard UIM cause the internal diameters of the runners are larger on the SVT one?
Sorry if this is getting confusing, I am trying to figure out what I should be expecting! ...

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Originally posted by Alan Coles:

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It's been shown the the SVT cams can certainly make good power with more air.

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(adding in To-Do list: Install SVT heads w/cams sitting on work bench)

Originally posted by Derk2000:

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ez - I could see how slowed air charge would lower hp, but aren't we measuring speed by using "cfm" ??? If our cfms are higher in the EH manifolds, wouldn't that mean the air flows faster?

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