Howdy folks, I just put another turbo on my truck and my exhaust temps have me very puzzled. My mods are in my sig and nothing has been changed except turbos. When I was on my stock turbo I could push it to about 55 psi, but my exhaust temps were only around 1600 tops. Then I went to a plain jane s300 with a ported 16cm housing, it ran hotter than the stocker during normal driving but on top it also ran about 100 degrees hotter, would make about 40 psi of boost. So tonight I installed a B-1 62-14 charger, in hopes of cooling down up top a little. Well much to my suprise I took off for my test drive and pegged my 2000 degree pyro at about 45 psi of boost. What am I missing here folks? I'd always understood that a larger turbop while it'll run hotter down low will cool better up top? Can anyone please explain what's going on here? It's got me flustered cus at this point I was honestly happier when my stocker was in.

 

i have no idea and i guess the other 30 people that looked at it dont either...
does it have any more power? does it gotta be broke in?

Sorry,
Jared

 

Try sticking a plate in it.

Your stocker at 55psi is sprinting to its death. It's overspeeding by over 20%!

A larger turbo won't always cool better up top. If your turbo is so large that you can't spool it, then you won't be getting the airflow you need, and EGTs will soar.

Conversely, if it's too small, then it will choke early and EGTs will soar.


I personally think that the turbo might not be the only thing at work here-- your pump tuning and how it's affected by the turbo might be another factor.

I'm no 12V guy, but from what I understand, any change in turbos means the the combination of DVs/injectors/plate/AFC should be re-examined-- at the very least, some AFC tweaking might be in order.

5x16s are a healthy amount of fuel. You really should be running twins.

JMO

 

ok, sorry I havn't updated my sig in while, currently I'm running a 100 plate fullforward, with a modded afc.

 

it sounds as if your getting it to hot right off the bat! try to take it out and instead of just mashing on it roll in to it and that should tell you if your over fueling it on the bottom end.

you said plain jane s300 a plain jane is a 57mm and you steped to 62mm??

a ported 16 housing would make it laggy and wouldn't spool up quick enough to counter act all the fuel your dumping.

plate timing and afc all need tuned!

sorry if this confussed you any hard to know from the monitor.
electronics are so much easier but you 12v guys can sing some rpms.

 

Hohn I think his latest turbo has a even smaller exhaust housing, he went from a 16 to a 14. That would raise egts would it not.

 

It should increase top end EGT, but average EGT would be lower...

 

while a 16cm vs a 14 would be hotter up top, I would also think that bumping up to the 62mm from a 57mm would counteract that and then some, because of airflow.

 

Yes and no. You are now pushing more air into the cylinder, which will lean it out and help EGT's. But you are now trying to push more air out of a smaller orificed, thereby increasing drive pressures and EGT's.

Have you got your AFC tuned in pretty good, or is everything loose/full forward? If you are dumping lots of fuel before it gets spooling, you have a lot of heat in there before it gets going, and its playing a game of catch up to bring down the EGT's.

 

That's the flawed reasoning that explains why so many guys are unhappy with their turbos.

A larger turbo with more airflow capacity NEEDS a larger housing. Period. Dot. End of story.

If you need airflow, the first place to look is by letting the engine exhale easier with a larger housing.

The problem with the stock HX35 is the tiny housing overboosts badly. I should have about 33psi with an optimally sized housing, but my 12cm unit is trying to make 38psi and then some.

Wastegating off the extra boost is inefficiency in action.

The first step to EGT reduction is always a larger, more free breathing hotside. THEN, you should consider a larger compressor.

Most diesel guys have it backwards, and they expect to magically get great performance from a huge compressor matched to a laughably tiny turbine housing intended to create passable spoolup where there wasn't any.

jh

 

I've got my afc pretty good now, did some work on it. Pulled the gooseneck today about 21K combined, it did ok as long as I manual shifted and kept the RPM's up. It's just the 3/4 to full throttle egts that are killing me.

 

wheres your plate located? any dv's? how big are your injectors? we run a 6 plate with 191, gsk, htt62/14 and still easily overfuel the top end. on this truck, the plate position and afc adjustments are being addressed to control higher rpm egt's. i think people underestimate the amount of fuel and when its delivered on these pumps. lots of fine tuning is needed. plus a 62/12 turbo is not all that big.