Engine/Transmission (1994 - 1998) Help. pyro and boost

[AndyJohnson]

When in 1,2,and 3rd gear boost and pyro perform about were they should with max boost at around 2400 rpm at about 28. But in 4th and 5th on accelleration i'm getting like 40lbs of boost and already at 1400 on pyro while cruising at what my spedo says is 65mph(more like 73to75mph) rpm is 2000 and boost is like 28. hit any gradual hill and boost is like 35 to 40. and pyro buries quickly if not very carefull and back out. The power is awsome with the boost but the pyro is not. in third i can hold almost redline for long time and not get to high of egt while i can get to high egt at 65mph if i'm not carefull. Thanks for any help ahead of time.

 

[AndyJohnson]

Does anybody have any ideas for me?

 

[mikel]

Ok, which truck? You have four listed in your sig.



I'll assume you are talking about the 12v since it has the most stuff listed in your sig. Is the turbo stock? If so then 40psi is too much boost, you'll be replacing a headgasket before long if you keep running it like that.



You can run 3rd

"for a long time"

to almost redline because 3rd isn't a load on your engine. In other words you can't really make the engine work with an empty truck in 3rd gear.



You are running way too much fuel for a stock turbo, but you get away with it in 1st, 2nd, and 3rd because you can't load the engine enough to see the problem.

"at 1400 on pyro while cruising at what my spedo says is 65mph(more like 73to75mph) rpm is 2000 and boost is like 28"

Are you saying that at 7x mph you see 1400 degrees and 28 psi of boost? Is this with an empty truck or are you pulling something? That isn't even reasonable for most things you'd be pulling. Have you checked for an exhaust restriction like a plugged catalytic converter or muffler?



Mike

 

[AndyJohnson]

yes i would be refering to the 12v and yes it is a stock turbo. I think it might be to big of a boost fitting. I gues i worded that wrong if i hit any kind of hill while going 70 75 i would hit 1400 and boost would be about 40. while cruising boost was about 28 and pyro 1000. this was with a 5th wheel trailer but its only about 6,000 lbs. max. I have talked to lots of people with same set up as me and there not running anywhere neer that much boost with stock turbo and no where near that hot. i think i just have something adjusted wrong or like i said to big a boost fitting. I'm gonna try stocker back in and see what happens.

 

[SRadke]

28 psi and 1000° while cruising with a fiver attached? Were the brakes dragging? Exhaust brake stuck on? Potato in your exhaust pipe? 28 psi at 1000° you should be making about 200-225 hp, that's way more than it takes to cruise flat ground.



-Scott

 

[AndyJohnson]

yeah your telling me. no brakes dragging or anything. it's not like it was hard to get and stay at that speed either it would get up to that speed quicker than others empty.

 

[SRadke]

Do you still have a kitty? You've got something seriously plugged up. Normally with those reading you'd be getting like 4 mpg.

 

[mikel]

if i hit any kind of hill while going 70 75 i would hit 1400 and boost would be about 40 Ok, that makes a little more sense. You're running too much fuel. Slide the plate back to get things in check.



while cruising boost was about 28 and pyro 1000. this was with a 5th wheel trailer but its only about 6,000 lbs. max. This is seriously not right on the boost numbers. Cruising on flat ground you shouldn't be seeing more than *maybe* 10-15psi at the most while pulling your trailer.



My thought is try sliding the plate back some and see where that gets you.



Mike

 

[AndyJohnson]

ok, but how is sliding my plate back going to get the boost down? And can you get more air to your engine without rasing the boost?

 

[AndyJohnson]

Oh and i still managed to get 13. 5 mpg pulling that trailer at avg. of 75 to 78 mph with a few big hills. i get about high 17's low 18's driving around town and that usually not the easiest on the pedal, i could be worse but not alot worse. thanks for all the help and will appreciate more.

 

[mikel]

Sliding the plate back will cut your fuel, that in turn will reduce boost. From what I have learned by talking to people that have broken alot of expensive parts, you're living on borrowed time at 40+ psi of boost. Using an adjustable boost elbow would let the wastegate open and lower boost also, but the with all the fuel you have to be running to make 40psi of boost you'll have heat issues even worse than now.



A bigger turbo will move a larger volume of air without the need for all that pressure, it will also so it without overspeeding. Right now your turbocharger is turning much faster than the people who designed it intended for it to turn. Sooner or later it will come apart and it may or may not take other engine parts with it.



Hope this helps,

Mike

 

[mikel]

Good mileage, by the way. I generally get 11-12 pulling my trailer and 18-19 on the freeway empty. I don't drive around town enough to have any mileage numbers for that.



Mike

 

[AndyJohnson]

thanks and thanks for the help. Yeah i definatly was not planning on keeping my boost anywhere near there I knew it was not good on my gaskets and turbo seals. and i don't run it above 30 unless i absolutly have to put my foot to the floor.

 

[bmoeller]

Part of the EGT issue is, that running 40#, the charger is heating up the intake air. I'd put on a 'gated 14 or 16 turbine housing, or go to a 40/35 hybrid. The 12is very restrictive at high RPMs.

 

[mikel]

Part of the EGT issue is, that running 40#, the charger is heating up the intake air. I'd put on a 'gated 14 or 16 turbine housing, or go to a 40/35 hybrid. The 12is very restrictive at high RPMs.

To take what bmoeller said one step farther, you should decide where you want to be power wise and (when your budget allows) buy a turbo to work at that level. My truck has only a #10 plate (just a little forward of center), 4" exhaust and 16cm housing and I hit 34-36psi of boost running it hard with my trailer. It's really easy to overwhelm the stock turbo, even with a larger exhaust housing when you actually use the truck to tow.



One of these days I'll be getting a bigger turbo, but for now I have to leave alot of power on the table so to speak.



Good luck with your truck.



Mike

 

[AndyJohnson]

thanks again guys.

 

[NHays]

Just a quick suggestion. Check and make sure your boost gauge is working properly before doing anything to engine. Had one go to the moon on me and spent hours on engine trying to fix it, turned out to be a bad guage. Sorry thing was it was brand new out of the box. it was autometer.

 

[HPetrat]

Andy:

Going by your sig, I have a 98 12v 5spd set-up almost identically as yours. Mine has 4" straight exhaust from the turbo down, 5" lift 35" tires and 3. 54 gears, BD #10 plate and DDT stage three injectors (stock turbo).

Running empty I can hit 35-37psi of boost but never see EGT's over 975*, even on a 16% grade. Boost will hit 35-37lbs but stays at 30-34lbs.

Cruising empty at 70 mph, 8-11psi boost and 800*EGT on level HWY.

When I tow my 30' TT at 8900lbs, on grades, I get 34-36psi boost (steady) and EGT's have never gone over 1250*



I agree with all of the suggestions posted, but after re-reading your sig, I see that your #10 plt is hand ground. I would suggest trying another #10 as the grind may be part of the problem. I tried 2 in my rig and both had the same final output on the dyno but one was quite harsh on the run-up (the slightly higher output plt was much smoother out of the 2). :-laf



I should also note that I run Autometer guages but prior to installation I did calibrate them at work and found that the boost was accurate to -+2psi and the EGT was -+ 10*.



Harry

Sorry, have had lots of suggestions on how to set up a sig, but it just doesn't seem to work.