Pardon my inexperience in this issue but bare with me:

If I have too much back pressure due to some type of choking of the turbo exhaust what does this look like on a dyno? Is it even easily seen on a dyno when tuning a car?

Would too much back pressure prevent a car from making power? For instance let's say something was lodge in the exhaust.

****EDIT*******
Dyno Graphs added.

 

Backpressure is an enemy of a turbo engine. The reason we get bigger diameter exhausts and components are to reduce backpressure and promote better exhaust flow.

So if you have a problem creating backpressure after the turbo, you will see a reduction in power/lower boost and you will also see slower spool.

If backpressure is very high it can cause high egt's as well as make the engine run poorly "even not run at all if exhaust is fully choked' , as well as shorten the life of the turbo as the load on the bearings will be increased.

 

So would an engine stop making power after it got to a certain boost level? If the car was on the dyno would you see this? Would there be some glarring issue on the computer that could be seen or is this issue hard to detect?

 

In all reality back pressure is the enemy of any engine trying to make power. Depending on how severe your exhaust is clogged it can bring about many different drive-ability issues. You will notice less vacuum at idle and lack of power. It wouldn't necessarily show up on the dyno and be recognized as a clogged exhaust issue if that is what you are looking for. In theory adding a o2 dump is reducing back pressure and that can be seen by power gains.

 

When would you start to notice the vacuum issue? If the blockage was maybe 40% of an exhaust or maybe 30% would you see it right away? Or would the car have to get to a certain level where exhaust gases are flowing fast enough through it to cause an issue?

 

So enough backpressure is like the proverbial wall to a motor. Could you tune the car and not gain any hp (maybe 1 or two hp) but the car drive fantastic?

 

At an electrical generation steam plant, at one end of the turbine is the boiler and piping conveying high pressure steam. At the other end is a condenser that condenses the steam to water. Both the high pressure steam and the vacuum created by the condenser power the turbine. If the condenser gets hot (not enough cooling water passing through it) the turbine loses power.

And, so it is with a turbocharger except no condenser. So all you can do to get the most pumping action out of a turbo is to allow the gases on the downstream side to escape freely. If the exhaust is restrictive this isn't happening.

 

It all depends on how much backpressure your talking about. If you stick a potato in the tailpipe its not gonna run worth a damn, but on the other hand the stock exhaust causes more backpressure than say a 3" open exhaust and a stock car runs perfectly fine.

 

So help us all out-- you had your car on a dyno and you didnt make as much power as you thought you would with some mod you made--am I close? Spell out your problem and everyone can chime in and help you out better if we all know what the issues are. There is a ton of good and bad with backpressure depending on the issue at hand.

 

Problem is the same one I've had for years and thought it would have finally been taken care of by replacing what we thought was the most obvious problem, the motor.

Jumping back a few yrs the car had a 4088 twin scroll made by ETS. Car made decent power for it being in Colorado. 33 lbs 675 hp. But at that time the car was out of fuel and wouldn't budge past 33 lbs. So we stopped. A few months later I got a new Magnus V5 intake manifold with dual rails (don't ask why). So at this point we had plenty of fuel but also at this time I moved onto a larger turbo that bolted right up to the original kit a 3794HTA again in TS format.

During the next few years up until just a few days ago the car even with the new turbo wouldn't make any power past 33 lbs.
Now you may point out the obvious things like cams, head, motor. Nope, all been changed and the problems continues with the new parts. Even changing states, tuners and different gas the problems continues.

So here's where Im at currently. Car is at Buschurs who just finished installing a brand new 2.4LR high compression 11:5:1 and the car made 624 HP @ 33lbs and Dave tuned it to 40lbs but didn't make any HP from 33-40 lbs where he stopped as it was pointless to continue tuning when nothing is changing.
So the car parts list is
2.4LR Buschur built/tuned/ installed
E98 fuel
STM650 cams
3794HTA twin scroll with the 1.15 a/r
Bushcur Stage III head bought from AWD
ETS 4.0 IC
maguns V5 manifold
Boomba TB
ETS LICP / UICP
FIC 2150 upgraded fuel lines with DP in the tank
AEM ECU
ETS 3.5' exhaust version 1 made in 2007 time frame with Varex muffler


Prior to the above parts list I had
Kelford 280
2.3 motor
same head
same exhaust
3794HTA TS but the 1.00 a/r
AMS 3.5 IC
Dual rail Magnus V5
Boomba TB
Was on E85

I even made a thread about this issue yrs ago but nothing panned out.
https://www.evolutionm.net/forums/ev...nd-720-hp.html

So same issue I've had but I've changed everything except for a few minor items that will now be looked at with more detail.

Any help that you guys can give I'll answer but again this issue isn't a simple one and changing out the cams isn't the issue since I've already done that. Or changing the housing on the turbo.

So now I have to look at other things that are odd ball items that are peculiar to my car.

Ask questions Please. I can clear things up as well if something was confusing above. I should be getting the car back this weekend though.

 

Have you boost leak tested the car? It's quite possible you're getting a leak, maybe at the IC, etc. Do you still have a cat? It could be clogged. To eliminate back pressure as being the issue, disconnect the exhaust and see who the power looks.

My initial guess was the head/exhaust ports, but it appears you have already replaced that. So it could quite possibly be a fluke bad weld on a pipe of the IC causing a leak.

 

Yup Buschur did a boost leak and everything was fine, no leaks.

No Cat for years.

Yup, odd ball things is what I need to look at now.

 

Also wanted to mentioned that Buschur said the car drives great, idles great and overall feels awesome and the turbo holds boost all the way up. So the turbo is good, no bent fins or rock chips. A/R can't be maxxed either as this turbo has been proven by numerous shops to make way more than what I am making at 40 lbs.

 

Once I get the car back here Im gonna take it to a dyno and disconnect the exhaust and see if that solves the issue. Or at the very least rules out the exhaust being the culprit.

 

Car is also hitting full spool by 5700 which seems a little slow.