stinkindiesel

I've got a 93 D250 with an auto and stock Holset turbo (16cm housing). It's only pushing 23 psi max. at WOT uphill with 5000 lbs in tow. What can I do to get up into the high 20's? I'm rolling plenty of black smoke, so it seems the fuel is there. Suggestions? Much appreciated!

dpuckett

It takes fuel to make boost, so you need to turn up your fuel to get more boost. BUT...... If you are only making 23psi with lots of black smoke, you have an issue somewhere. How is your air filter? Fuel filter? What about the last valve adjustment (book calls for 24k, I think). Those will affect smoke.

Also, may not hurt to check timing, and injectors for spray and pop pressure.

Do a pressure test on your intake system from the turbo to the intake manifold. If there is a leak (notorious along the seam from the core to the tanks of the intercooler), it will lower apparent boost and can increase smoke.

What kind of EGT are you seeing, and where is the probe?

Daniel

stinkindiesel

I'm seeing 1100* at 70 mph up a fairly steep SoCal freeway grade with 5000lbs in tow; probe is on exhaust manifold before the turbo. Air filter is new BHAF, fuel filter is 5k old and the intercooler has no leaks- I had it out 6 mos ago and did a pressure test like I saw on this forum. Unless someone has a really cool idea like installing then blocking off a wastegate I guess I'll adjust the valves this weekend. Dang.

DanMan

Is that with the tranny in drive or OD?

Mine's got the stock 21cm housing and the best I see is 16lbs The pump is tweaked.
I've got a 18.5 housing.... waiting to be installed

stinkindiesel

That's in Overdrive with 3.05's out back. So... should I be satisfied? Naaah. I need more, please.

sdstriper

Check throttle travel. You can gain more throttle travel by backing out the high idle adjustment screw and shimming the pedal out from the firewall mount.

I am seeing 30+ psi boost with a stock H1C/18cm2, non I/C, pump is tuned but I have yet to install the 3200rpm spring...

Any chance your fuel is the limitation? Never ran bio myself.

JD730

23psi is all my 93 would do on stock injectors. I don't know if the stock injectors will flow more fuel or not.

gman07

Before I ground the AFC lever and bent the pedal, I was only seeing ~25 psi. Make sure you're getting full throttle travel.

Is it still smoking after the turbo spools or only when you get on it at low boost? If the turbo clears up the smoke, then it's probably just not enough fuel.

TexasHardcore

Get an HX35 if you're looking for more boost and useable power. My old 1st gen made 23psi on the stock 21cm2 housing and H1C turbo. With the HX35/40-16cm2 NW setup, PODs, 4" Downpipe, 5" exhaust, BHAF, 3200GSK, Fuel Pin, & Pump Tweaks the truck made 46psi boost, and EGT's were never over 1100 even when laying into it or towing heavy. Good for 341hp/842lbft at the wheels and 23mpg on the highway with 3.55's.

JD730

46psi I believe, but I'm calling BS on 1100 if it was in the manifold. I could bury a 1600 degree pyrometer with POD's and a HTT stage IV.

rbrettctd

What size dp were you running though? With his exhaust setup, he probably had a 200* or better drop over stock.

DieselSmith

how long can you hold 1300+ egt's before you begin melting pistons?

1stGen545

All day long at 1250 acording to Cummins. You can run over 1600 for short times and be fine. The guys that melt pistons usualy are holding realy high (1400 +) towing for long times. It takes more to melt a piston than most guys on here will act like.

TexasHardcore

4" Downpipe, pyro was pre-turbo. I never ran the truck on long hard pulls like a dragstrip, sled pulling, or pulling anything really heavy other than some big 50's cars. But the EGT's never got up there.