What does backpressure do to a motor?

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Jun 24, 2013 | 10:42 AM

#76

Joshs EVO

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From: Thornton, CO & Pasadena, MD

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Originally Posted by way2qik

Well, at this point all you are doing and can do is guess... If you want to change that, you will have to check backpressure. What I did was weld a port onto a header tube so that during a dyno session I could hook up a gauge to measure back pressure during a pull.

Also, I'm not wanting to argue or go against anything Aaron told you. But, I would just say that you need to remember that you have a pretty good sized engine at 2.4L. On a 2.0L that 1.15 hotside might be enough, but on a 2.4 it may be a restriction at higher pressures. Also, you have a higher compression engine, which needs a free-flowing hotside. Just some things to consider...

I would guess that you are seeing at least 2:1 in terms of backpressure. By the time you hit 35psi it might even be closer to 3:1, which is horrible and will certainly kill power at higher boost pressures. For a street car I like to see that number down closer to 1.5:1

Found it Way2Qik:

So should it be welded into the collector or to just one of the header pipes? Are you using a wideband to do the measuring of the pressure? I most likely will have the shop do this.

Jun 24, 2013 | 11:01 AM

#77

SaulHudson

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Originally Posted by Joshs EVO

https://www.evolutionm.net/forums/ve...ure-plate.html

Jun 24, 2013 | 12:02 PM

#78

Joshs EVO

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From: Thornton, CO & Pasadena, MD

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Originally Posted by SaulHudson

https://www.evolutionm.net/forums/ve...ure-plate.html

Nice, something I can do. No welding needed. Will be calling them today to order.

Jun 24, 2013 | 12:10 PM

#79

Dynotech Tuning

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From: Seekonk, MA

Unfortunately our back-pressure plate only works if you have an intake manifold with an EGR mounting flange and the EGR port on the head hasn't been plugged.

I thought I saw that you had an aftermarket intake manifold?

-Jamie

Jun 24, 2013 | 01:09 PM

#80

Joshs EVO

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From: Thornton, CO & Pasadena, MD

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Originally Posted by Dynotech Tuning

I do have the Magnus V5 intake manifold. Dammit.

Jun 24, 2013 | 02:27 PM

#81

Dynotech Tuning

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From: Seekonk, MA

Just had an 1/8 NPT bung welded to the collector on the exhaust manifold and you can use an adapter fitting to get a back pressure reading. If you search on google you can find a lot of info on it.

-Jamie

Jun 24, 2013 | 05:14 PM

#82

Joshs EVO

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From: Thornton, CO & Pasadena, MD

Well bit of an update. As much as I would have liked the exhaust being the issue or the flex joint being the problem it's not. I dropped the test pipe and the flex joint is only a few inches away found nothing impeding the flow of gases. It was a slim chance but since Brian @ FP suggested I look into this I can say that I have ruled this out. I can see daylight when looking down the remaining exhaust towards the rear of the car and again nothing impeding anything.

So the chance that something is further forward from the flex joint it very slim. I got a decent look up the down pipe and there's really nothing up it so I doubt there is anything from where I could see to the turbo.

So after talking to a few people the head will be coming off and I will be rebuilding it with new springs, valves. Going to go Kiggly everything. The head and it's components is at least 3 yrs old but closer to 4 yrs I think. So freshening them up won't hurt.

But I think before I do this I will have the bung welded onto the collector and have some readings taken and narrow it down even further.

Last edited by Joshs EVO; Jun 24, 2013 at 07:37 PM.

Jun 25, 2013 | 06:39 AM

#83

Joshs EVO

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From: Thornton, CO & Pasadena, MD

Would this pressure tester be good?

Amazon.com: Westward 1MZT5 Tester, Exhaust Pressure: Automotive

Or would this one be better?

Tool Aid 33600 Exhaust Back Pressure Tester - Amazon.com

Or even this one
http://www.ebay.com/itm/Backpressure-Tester-oxygen-sensor-adapter-O2-exhaust-Back-pressure-gauge-/330935226192?pt=Race_Car_Parts&hash=item4d0d46cf50&vxp=mtr#ht_558wt_932

Last edited by Joshs EVO; Jun 25, 2013 at 06:43 AM.

Jun 25, 2013 | 07:58 AM

#84

Dynotech Tuning

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From: Seekonk, MA

Those wont work because you need to test the pressure BEFORE the turbo, between the head and turbo itself. The O2 sensor bungs are after the turbo.

The kits you listed are good to show if the exhaust system itself is restrictive though.

-Jamie

Jun 25, 2013 | 08:20 AM

#85

Joshs EVO

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From: Thornton, CO & Pasadena, MD

Do you have one in particular that will work? I thought as long as I welded the bung onto the collector it didn't matter.

I called you (Jamie) yesterday and left a message.

Jun 25, 2013 | 09:17 AM

#86

Dynotech Tuning

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From: Seekonk, MA

Most people just weld an 1/8NPT or 1/4NPT bung onto the exhaust manifold and make adapter fittings using a long run of copper tubing to help dissipate the heat before it reaches the boost sensor/gauge. Dont forget that the temps will be in the 1600*F range in the exhaust manifold. Make sure you get a boost sensor or gauge that can read at least double the boost you run in the intake manifold.

-Jamie