Is there a known HP to be gained with exhaust cut outs?

pass1over

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maybe I'm reading the graph wrong, but I see it breaking 300 ft/lbs at 2600 rpms. I would imagine the 600 or so rpm delay difference between the turbo and your PD setup is turbo lag. I could be way off base here though.
 

Pentalab

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maybe I'm reading the graph wrong, but I see it breaking 300 ft/lbs at 2600 rpms. I would imagine the 600 or so rpm delay difference between the turbo and your PD setup is turbo lag. I could be way off base here though.
Ur right, I was reading the wrong graph. There is not much, if any, for the dreaded...'turbo lag' either.
The boost ramps up very quickly when you look at the boost graph.
 

pass1over

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Ur right, I was reading the wrong graph. There is not much, if any, for the dreaded...'turbo lag' either.
The boost ramps up very quickly when you look at the boost graph.


You are correct. The hp/tq numbers do ramp up pretty quickly. I've never owned/built/tuned a turbo car. But now that you say that, it makes sense. I guess if it was lagging, there would be a long flat spot before it ramped up?

As for rear mount turbo setup, I had a friend with a C5 vette, when I lived in Lexington 10 years ago, rear mount turbo setup and that thing didn't really lag at all. It ran low 10s I think, daily driver.
 

AHaze

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Interesting to note, it doesn't hit 300 ft lbs of TQ, till it gets to 3800 rpm. I'm > 300 ft lbs @ 2 krpm with a M90 and 5.7 psi boost..(with an automatic). The turbo setups appear to crank out globs of hp/tq at higher rpms...but doesn't have the big tq hit at the bottom end...like a PD blower does.

I think you're looking at the wrong line but either way, you will likely make more torque at very low RPM with your little M90 than a turbo setup would.
Another interesting thing about turbo setups is the boost threshold RPM changes fairly drastically since turbos are load dependent vs. superchargers which are RPM dependent. I didn't fully realize this until I started datalogging my DD Subaru. On a 3rd gear pull, that car hits 10 PSI at roughly 2750 RPM. In 4th, it will hit 10 PSI nearly 200 RPM lower.

maybe I'm reading the graph wrong, but I see it breaking 300 ft/lbs at 2600 rpms. I would imagine the 600 or so rpm delay difference between the turbo and your PD setup is turbo lag. I could be way off base here though.

I think you've got the correct graph line. The minimum engine RPM required for the turbo to make significant boost isn't "turbo lag" though. That's the "boost threshold" which as I noted above, is not always the same. Turbo lag is the delay between hitting WOT (at an engine RPM above the boost threshold) and the turbo impeller accelerating to whatever RPM is required to make peak boost.
 

Dino Dino Bambino

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Interesting to note, it doesn't hit 300 ft lbs of TQ, till it gets to 3800 rpm. I'm > 300 ft lbs @ 2 krpm with a M90 and 5.7 psi boost..(with an automatic). The turbo setups appear to crank out globs of hp/tq at higher rpms...but doesn't have the big tq hit at the bottom end...like a PD blower does.

You're looking at the baseline dyno run. With the turbo it hits 300rwtq at 2600rpm and it's over 400rwtq from 3500-6100rpm. Maximum boost is 9psi but it hits 7psi as early as 3100rpm. I like the fact that boost ramps up linearly up to 3100rpm so you don't get that sudden hit that could send you spinning sideways into a ditch and turn your pants brown.
The turbo itself is mounted on the driver's side between the fan and the engine. This necessitates the PS pump reservoir to be relocated to the driver's side on the front of the strut tower, and the '05-'06 models to be updated to the '07-'10 cooling system set up. With all the pipework for the hot side, cold side, and intercooler, the engine bay is absolutely jam packed and the underside looks like a nest of snakes.
 
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RED09GT

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The reason why the post-turbine exhaust has to be as big or short as possible for max power is due to the fact that the exhuat leaves the turbine wheel in a spinning motion rather than in a straight line like a conventional exhaust. This is why every youtube hero has a front bumper exit on their turbo "street" car. Other tricks that you can do is to have a bigger exit at the turbine to allow some space for the exhaust flow to go from a spinning/turbulent flow back to a laminar flow.
I'm going to up the discharge of my downpipe to 4" and reduce back to 3" to get past the k-member and keep my exhaust routed back to the rear as I don't want to smell like exhaust everytime I take my car for a drive.
 

XJCasper

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Lito will do a vastly better job than BAMA for sure.
The most restrictive parts of the stock exhaust are the stock manifolds and cats. Replacing anything after the cats will result in minimal HP gain.
@XJCasper do you still own a Jeep XJ? I sold my '92 XJ 5-1/2 years ago after more than 21 years of ownership. You might recognize it:

http://www.jeep4.0performance.4mg.com/

Thank you
No and Yes... LoL
My son talked me out if the Jeep about 6 years ago. So no I don't. But it's still in the family.
 

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