neal1980

Hi,

I have a Iron forged 383 LS with twin 70mm on3 turbos 0.68 exh. (ls9 cam) tr6060 6 speed manual, 3.55 rear end.

Its currently mapped to 10psi.

I tried to use the car hard yesterday and was surprised that I couldn't make the 10psi boost until I was almost at the end of 4th gear and pressing on hard. Below that it was almost like 2nd gear 5 psi, 3rd gear 7 psi, 4th/5th gear 10psi.

I have an eboost 2 which is setup just as high and low boost (nothing gear based) just 2 setpoints adjusted correctly.

Could it be the turbo's are too big ?? My cam is rubbish or maybe a wastegate problem - diaphram?? (I did confirm the wastegates were not stuck open but that's all)

I have checked the cold side with compressed air and I cant find any leaks.

I thought with a 0.68 exh they would light up much faster.

Thanks

Neal

coltboostin

I dont think its the turbos. Cam, maybe? I'd try more gate spring first.

Here is my car on a stock 5.7, twin On3 67s. Same turine wheel and .ar. I can see 10psi in first no problem.

stevieturbo

Good to hear the cars going, even despite boost, it's bound to feel good ?

What w/g springs ? How is the controller plumbed ? As a test, you could try and remove any signal lines from the gate and run spring only, but do set a tight boost cut in case things did change a lot and you arent ready to let off.
But it would let you see if a different plumbing config might be worth trying if it did make a big difference

If you apply the brakes in 4th gear to hold more load against the engine at lower rpm and slow rate of rpm increase, does this change the rate boost comes on ?

And what is tuning like ? any logs with AFR, timing etc during spool ?

As for things appearing laggier in lower gears, that is fairly normal and given what you describe in the higher gear, not that surprising the lower gears seem lethargic with boost ( although I'm sure the car is still accelerating )

Even with my heavy car, the engine just accelerates faster than boost picks up in lower gears compared to say 4th or 5th from a similar rpm but even with lower boost..it's still far more power than traction so just isnt a problem.

Their spec is a little odd...says 61mm and then 70mm for inducer ? 99mm exducer is pretty huge and it would be a very heavy wheel so not surprising it would be slow to respond

http://www.on3performance.com/shop/o...-turbocharger/

Turbine side sounds ok though. The smaller turbine housing can only do so much though.

A better/bigger cam could definitely improve things too....although I'd nearly guess a pair of smaller turbos might be easier to swap out than the cam ! lol

svslow

I would vote cam as well. The LS9 cam is pretty lazy down low, especially with a stick car.

LJMSJohn

the cam has -22 degrees of overlap.... odds are your tuneup isnt sorted well for spooling either.

stevieturbo

The cam will make a difference, but from the info given so far, it is way more than just a cam issue.

I would definitely have gone for smaller turbos ( and more modern smaller turbos would probably flow a lot more air than those On3's anyway, as well as spooling much faster )

And given the build...I envisage it being a nightmare to change the cam, hence saying it might be easier to try different turbos, albeit a bit more expensive.

LJMSJohn

Uhhh those turbos have a P trim turbine wheel... Theres nothing wrong with the turbo selection... lack of overlap, and probably a tuneup thats fat and cold.

neal1980

Hi Steve,

The car is unbelievably fast as it is but just thought it should hold full boost in the lower gears as well.

After writing this post I stripped the wastegates and it looks like the springs had gone a bit soft they were starting to crack at 3psi tested off the car. I had some havier ones which when pressurised off the car didnt open till 10psi. However when they are not installed I can only get to about 7 psi in 4th gear until I switch the boost controller on.

I tried again in the lower gears and dont hit the full 10psi still, I hit it hard in 1st and 2nd it got 3psi then from 3rd it went more but at that point it tried to chuck me off the road lol

Im running megasquirt so could get some logs tonight of pulls through the gears.

The LS9 cam gave me a lovely idle but ultimately if this is leaving alot on the table I dont mind switching it out over winter time. I must have nice idle though not lumpy :-)

I will log tonight and report back

neal1980

Is there a cam that you would recommend that would be better ?? All I ask is a nice steady idle not lumpy :-)

I will get some logs up asap that might mean more to people.

Thanks :-)

67Firebird455

iTrader: (27)

Talk to Jarrett (stock48), he's got great options. Many find the Triple 12 to work really, really well and still idle well.

stevieturbo

IMO nearly all of the "turbo" cams about these days should idle well. Few seem to go too big on duration/LSA/overlap etc now whereas before some may have

I think mine is in the 220-230deg region around 116 LSA ( LLSR though ) again as I had same idle needs as yourself and it does that well, and passes MOT here no bother at all, although with the older car I do have higher limits.
I think my CO was easily around 1.5-2% and HCC 100ppm !! So I do have room for quite a step up if needed.

That also said, I really dont think overall things changed much from the LPE GT9 cam I used previous. Again another super smooth idle cam.

But Jarrett's cams mentioned above do seem interesting and many get great results from them, although I think most are on smaller 4.8's or 5.3's ?
But no idea on their idle or MOT friendliness ( or of that is a concern for you )


As for gates/springs. Are you using the same pressure gauge to confirm gate opening, as also the MAP sensor calibration ? May be worth checking
I've seen some gauges be miles off ! So always worth ensuring all the gauges you're using..at least read or are calibrated the same

But pretty much with the 7-7.5psi springs in my gates does yield the same boost pressure when run on spring only ( and boost ref to bottom chamber )
But as with everything there are variables that can affect this so a couple of psi difference here isnt a big deal.

LJMSJohn

You mean you don't want lope?? lol

you could try my stage 1TT cam. 222/227 on a 112+4.

it has 0 degrees of overlap at .050... so it is going to have a significantly improved midrange. Idle might be a little lumpy... we could also do a custom say like 222/225 on a 114+5

The BallSS

iTrader: (9)

Just some cam input.
230/230 .609/.609 115+2
All the lope lol.

forcd ind

iTrader: (7)

I noticed sometimes I build lower boost in 1st gear, I just kind of felt the engine could RPM faster than the turbo could-once I am in second gear, its a longer time frame than 1st, so it would build more boost-could be a lot of things, that was just my opinion, I may be way off.
Once I get to the track, have traction, then I can data log and see what actually it is doing.

Johnv

What diff gears are you running ?
Turbos like load.

gsteele

I would love for someone to explain who came up with that idea and exactly what it means.

stevieturbo

It was explained already

If you rev the engine in neutral.....you'll make no boost.

If you rev the engine in 1st gear...it may make some boost.

Do same from same rpm in 6th gear...it will make boost at a much much lower rpm

It's almost a case of which will spool up faster, the engine or the turbo. Loading the engine up slows the rate of rpm rise....which gives time to spool any turbo.

Same reason why inertia Dynos suck for turbo cars, they may not load the engine enough for any boost profiles to mirror what may happen in real world conditions.

gsteele

^^ Somehow I get the sense that when most people use that phrase they do not mean to be describing the obvious. You may be right, it is probably that simple.

Forcefed86

iTrader: (4)

Have you put your hand at the WG exit with the car running and confirmed they don't leak any? Maybe have someone rev the engine a bit while you do it? I've seen more than a few china gates leak around the valve.

I'd pull the bottom WG port reference and leave the top attached directly to full manifold pressure to ensure the gates are closed and stay that way. Then do a few quick low gear pulls and see if it's more responsive. Be careful, it will over boost this way if you don't let off quickly.