Peak power on a 3071

[campbellju]

Was having a play with my G-tech on way home. Its not an exact scence but after 2 Horse power style runs, it showed peak HP around 6200pm. I thought ths was a little low an I have higher lift piper cams fitted, going back a few years peak hp was nearer to 7K on a T28. I've got the smaller .63 A/R turbo dynamics internal wastegate turbo.

I'm guessing I need to go out again and check to see when the boost drops off but I haven't noticed any significant fall.

So I'm thinking:

1 Its normal even at 1.6 Bar with this turbo

2 Its been mapped prudently to stop misfires at high boost/rpm

3 My standard elbow is causing a restriction above 1.xBar.

The nice thing about the standard elbow is it stops boost surge, and why I wasn't rushing to get rid of it.

Any thoughts appreciated.

Jim

 

[stumo]

I think you need to use a spell checker or are you trying to chav it up a bit?

 

[campbellju]

my wireless keyboard is playing up, probably needs new batterys, I edited once then gave up trying, had another go just for you Stu ;-)

 

[stumo]

yeah yeah :roll:

 

[campbellju]

Finally found this from Stu's car, its similar in that my hp curve almost flat lines from 6000 too and by 7000 it is dropping away. I'm running 1.6/7 Bar where as Stu was around 1.4Bar here. I've also read blurb about restrictive exhaust housings on the .63 A/R 3071. Is my restrictive exhaust housing having more of an effect above 6K?

http://img.photobucket.com/albums/v341/sturat/scan.jpg

I still wonder if 2 and 3 are issues on my car?

 

[stevepudney]

I think your standard elbow is the power leveling off problem. Although I don't have a Dyno print out to show it, but I have the Janspeed 3" complete system and when accelerating in forth (WOT) it just pulls and pulls, the power doesn't seem to start to plateau off at all.

 

[CruiseGTi-R]

what weight and transmission losses did you stick into the g-meter and is the sensor trimmed?

Mine changes a lot depending what I stick in. Before calibrating it gave me 956bhp :shock: :-D .

 

[campbellju]

what weight and transmission losses did you stick into the g-meter and is the sensor trimmed?

Mine changes a lot depending what I stick in. Before calibrating it gave me 956bhp :shock: :-D .

I used 1250kg to include me in the cars weight. I've got the G-tech pro that ignore transmission losses and provides real world horesepower that includes drag as well!! The readings tend to be a lot worse than a dyno.

I'm not sure about my pitch factor, that you can setup. You're meant to calibrate that at a drag strip.

Steve, thanks for your comment, its my gut feel too. I was thinking if I drop the boost then the car might make similar HP higher up the rev range with less boost drop?

 

[Rishi]

You will be getting backpressure with that std elbow... Righer rpm will mean more gasses to pass in any given time which the std elbow will struggle to flow...


Rishi

 

[campbellju]

Right, jobs to do list;

replace turbo elbow.

Probably won't get chance to do it before the rolling road but you never know.

 

[ashills]

with a twin dump pipe and 2.5 straight through exhaust i had full power to the red line on my old 3071

 

[campbellju]

with a twin dump pipe and 2.5 straight through exhaust i had full power to the red line on my old 3071

Is the twin dump pipe where the elbow has an exit for the main compressor and a seperate smaller exit for the W/g?

What was full power on your 3071?

 

[ashills]

yeah thats right 2.5" main outlet and a 1.5 " for wastegate then joined back together before it met front pipe

full boost was made around 4k from memory

 

[campbellju]

Thanks, this type of design seems to be the way to go. I just need to decide whether to fab one or source/modify one.

 

[stevepudney]

yeah thats right 2.5" main outlet and a 1.5 " for wastegate then joined back together before it met front pipe

full boost was made around 4k from memory

4K :shock: , I get full boost way before that, desipte it being a bigger turbo my 3071R (.86 ar turbine housing) spools way faster than my last turbo (2871 = Turbo Dynamics MD214).

I get full boost before 34 - 3500 rpm. In my opinion a big 3" single outlet is the way to go, on boost the turbo wants least restriction possible.

 

[ashills]

may have been earlier mate it was 2 years ago lol ill see if ed has any data logs of car

 

[Mr GTiR]

In my opinion a big 3" single outlet is the way to go, on boost the turbo wants least restriction possible.

I was told the same thing by Ian as i wanted a split twin dump pipe set up. Now i'm just going for a 3" elbow.

 

[youngsyp]

Afaik, the only reason to use a 'twin' dump pipe is to reduce turbulence as the gas exits the turbo, into the turbo elbow therefore effecting gas speed etc... How great an effect would the two streams of gases meeting have on each other ? I guess the gas from the turbine would be coming out very fast as, it's literally being thrown out by the turbine blades where as, the gas exiting the wastegate is probably more restricted, at lower pressure and so slower. Would the gas speed from the turbine over come this though and not be tangibly effected ? Also, the wastegate wouldn't be open for exteneded periods of time so, again, is there any need for a separate pipe for it ?!

I would have thought the single big bore dumpipe would be better for initial response and reducing lag as, it's providing the maximum gas flow to spin the turbo, when it's needed, I.e. at the lower end of the rpm range. However, it would also be better high up the rev range as, it will be shifting the most gas out of the turbo, all the time. The single 3" bore pipe does seem like the optimal choice, it certainly works well on the last two turbo cars I've had !

Just a thought or two !

 

[campbellju]

Here is a guy with a thought or 100. His twin pipe debate is all to do with backpressure at the turbo outlet like you say. The WG isn't just open or closed unfortunately and spends most of its time in the middle. When I setup my actuator I was surprised at how early the WG starts to open.

http://www.max-boost.co.uk/max-boost/exhaust/exhaust.htm#backpressure

Its got to be taken in context so you need to start at the top of the page rather than fast forwarding to elbows. He is suggesting a twin pipe for a few feet, not just 6". re-reading his article, my understanding is the sinlge 3" outlet will perform better than the standard elbow but is not the "optimal" solution for an internal WG. The optimal solution is to join the two pressure streams later and more slowly. I think he's also saying if you can be bothered to do this then you should just fit an external wastegate instead.

 

[youngsyp]

He is suggesting a twin pipe for a few feet, not just 6". re-reading his article, my understanding is the sinlge 3" outlet will perform better than the standard elbow but is not the "optimal" solution for an internal WG. The optimal solution is to join the two pressure streams later and more slowly.

That's the impression I got from reading around the same subject a few years ago when deciding on an exhaust for my GT Four. The suggestions seemed to be (in the context of the GTiR exhaust) to rejoin the two pipes at around point just before the flexi starts, at a very shallow angle, if memory serves me correctly ?!