Ok so we have this Sky Redline LNF.....

It's just a full PITA! It's an auto, with no real gear selection other than "I", no auto support from HPTuners yet, so dynoing it is next to impossible. We finally got it to give us semi correct numbers with 238whp (~24psi) stock. So we move on.

We built a full T3/T4 turbo setup on it using a T04B-SH trim turbo (58mm ind/70mm exd) with a .68AR turbine, external wg, the whole nine.

Now I fully understand the HPT strategies, and the tuning side, I've got the AFR's where I want them, I can play with timing, but the issue is we seem to have hit a road block with the power.

We first started with 12-13psi, and cranked out a cool 254whp, +16 from stock with WAY less boost, cool. This turbo seems to be WAY more efficient. Then we started bumping up the boost/power. 300whp with 17psi. But then we hit ~24psi and it seems to stop at around 335whp. We peaked one run at 345whp, but it's not repeatable. It doesn't want to seem to go past 24psi. We changed the WG springs to stiffen it up and help fight the exhaust back pressure....didn't help. (MBC with a 38mm WG BTW). I disconnected the WG, didn't help, the exhaust still blows it open. Disconnected the exhaust thinking maybe back pressure from there....didn't help.

We noticed the manifold is getting cherry red hot....so we redesigned it to a simpler one with thicker sch 10 wall. Not it's not as bad, but still redish, and I can tell the EGT's are through the roof. I added fuel, no help. Played with timing, no help. And no matter what I do it seems the EGT and exhaust back pressure are too much once we hit the 335whp range and 24psi. We peaked a bit higher on the old turbo, though no where near the flow or power, and of course didn't hold it till red line.

So since I don't know as much of the LNF as I should, I've come here. I know a few of you guys on here are peaking numbers higher than this, so what's the secret? What am I missing?

From what I can tell these engines don't like to flow all that much, being a 2.0L and 20+psi hitting only 240's. As well as these turbos we've used many times before on similar sized engines (making more power), and this one seems to display a bit of compressor surge (occasionally, and not too bad.) We were really aiming for the 400-450 range, and this turbo should be perfectly sized (going by other 2.0L, I'm clueless on the LNF).

Also I should mention we are at 6000ft in elevation, so with the correction factors, our fuel requirements aren't as stringent as most.

Any help would be greatly appreciated, if someone could just point in the right direction, or point out something I may be missing?


CK

 

Contact ChevyCobaltss3. Great tuner, I'm sure he can set you in the right direction.

 

Is he on this board?

 

That's his user name... chevycobaltss3. I'm local to you... kinda... he did my tune on my Cobalt SS/TC. Not sure how much power it's putting down, but it runs a 13.1 @ 110.5 at Bandimere on stock turbo with E85, so I'm sure he can help you.

 

i believe guys with zfr are hitting 400whp around 24psi. u using stock manifold? if so is the turbo twinscroll to match the manifold? dont see why u shouldnt be making more. what a/f ratio u running?

 

You have the 3bar map sensors?

 

We've tried a couple manifold designs (all custom), the first was a ramhorn style, but where it made it's bend back, it was restricted down, and that was the "source" of the initial glow, so we scrapped it and went with a simple proven "log" manifold, SCH10 weld els.

Yes, it has the 3Bar maps, and I've played with the AFR's everything from the lean that these engines like of ~12.5 to the normal 11.5's. I've even dipped lower to see if it would quell some of the excess heat and maybe drop pressure (10's), and nothing seemed to effect it.

I really would have assumed we'd be closer to the 400's with this boost (especially with the great results we were getting at 13psi) , or at the very least able to go past 24psi.

I'm assuming I could hold the wastegate closed, but the engine already seems to be struggling with heat/pressure here, I don't want to make matters worse. I just want to understand what's really happening and why the engine is so prone to do this? Is there a problem with the head flow on these engines? When I look at the head's ports, they're the smallest that I've ever seen. I think even my lawn mower has more port flow! LOL

CK

 

I only know the basics of turbos, but if there is too much back pressure wouldnt you want to try a bigger exhaust side to flow more outta there? Sounds like a nice setup regardless, best of luck!

 

You have any fuel support mods?( i.e. 5th injector or cams with bigger lobe for hpfp)

 

He won't need it at 6000ft altitude.

 

I'd really have to say it's not a fueling issue, as I have the ability to add more/less at will. It doesn't seem to be a timing issue either....and it's def not an issue with the w/g duty, as we're all external and using a mbc.

CK

 

Check on the hp tuners forum. Area47 would be a good person to ask.
Don't have a lnf so I am not sure if the tables are there but if they are you could try playing with the exhaust cam timing.

 

try adding any cooling mods such as meth injection?

 

i just wanted a reason to use it.

keep the afr about 12.5-12.6 timing will vary due to altitude differences between here and there. it may just be out of fuel. have you messed with the injection timing tables any? the two people i would actually reference to are gmtech and terminator2. im more of the lsj guru than anything around these parts.

 

I'm not out of fuel, I know that. It's sitting in the 12.1-12.2 range, but I more than have the ability to flood the hell out of it still. I can increase the injection timing and give it 10's for AFR's. To me it's really more like a flow problem, like the engine (or head) just REALLY doesn't want to flow what I'm feeding it. But I've never really seen this before, but I've also never seen ports as small as these.

I thought there was alot of people pushing these things well into the 400's and I was hoping I could find one on here to help me out. Someone to say "Hey ******* you have to do this..."

Area47, let me ask you this, how much are the LSJ's really different from the LNF besides the DFI? I think the exhaust ports are at least the same size on the heads, are these ever a problem for you guys?

CK

 

stock head can make 490whp. the restriction starts on the exhaust side. like 90% of the gm cylinder heads. ignore the indicated idc. watch msec. you have a small window to work with. 6-7 msec in most cases. if you're over this, you're losing power and pissing the injectors off.

 

I'll look at the logs for the idc, but I'm monitoring the afrs, and I'm plenty good there. I know what the signs of running out of fuel are, and other an the egts , it's not exhibiting it.