Engine/Transmission (1994 - 1998) 4 mpg less w/new turbo

[egould]

I have recently upgraded to a PDR hx-35 and a 14cm

wastegated housing on a 97 3500 with 4. 10's and a five speed. Unfortunatly,the new turbo has had an

opposite affect to what I was trying to achive!The

egt's have gone up 50 to 75 degrees and my fuel milage has dropped 4mpg under heavy towing compared to the stock hx35/12. My truck is heavily

fueled with a #10 plate and 370 injectors,but I drive it VERY carefully when towing. The past trip I was towing 11,000lbs. about 65mph(2200rpm)

and averaged 8. 5 mpg. It used to do about 12mpg with a load of this weight. Can not find any boost leaks and I have a 4in. exhaust and AFe intake. Could anybody share any

ideas or past experiences? Thanks in advance for any help!

 

[DRAG DIESEL]

Yeah... . the slower you spin the turbo ie: 14cm2 housing the higher the egts will be. Never understood that mod for towing... now if your talkin' HP???!!!..... Bigger the better (to a point)

 

[Bob Wagner]

what was you boost pressure while towing? And what was your mileage towing? MPG



And post some details of what you were towing

 

[bmoeller]

I think it is the 14 housing that is hurting you.



Had the same thing happen on a Mack truck. Had to replace the turbo, but the new one they gave me had a bigger turbine housing. Lost 4-6 psi. peak boost, and the EGTs climbed very fast, peaked about 2-300* higher than normal for the conditions. Made the engine (that was already under-powered) a REAL dog. Lost alot of power. Mileage went down also. Got the correct one and all is well.

 

[nascar mark]

Originally posted by egould

Can not find any boost leaks. Could anybody share any

ideas or past experiences? Thanks in advance for any help!

Did you have the turbo to engine charge air system pressurized? If not you can't be sure there isn't a leak in the system. I would first look at the o-ring (usually orange) between the compressor housing and the 90 degree elbow that runs to-wards the inter-cooler. This is a common spot for boost leaks when changing out turbo's. Check it out.

If your still having a problem, give me a call at the shop.



Mark

PDR

 

[egould]

Thanks for the replies everyone! Bob,I was towing a 70hp tractor on an 8 by 20 tri-axle trailer (GI hitch type). Tractor and trailer together weighed about 11,000lb. At 65mph on flat interstate my boost psi was around 16. A bit of an incline and we were into the low 20's and up to 30psi on hills. A full tank of diesel got me 240 miles (all interstate,no back roads).

Mark,I had my truck at Garmon Diesel in McDonna,Ga. a few days ago for a dyno run(wich got cancelled because of rain) and Jeff Garmon drove my truck to see if he could help out. He too thought that I might have a boost leak but we couldn't find one. I was very carefull when I installed the turbo and that orange o-ring you mentioned looked in good shape. To answere your question though,I have not pressurized turbo to induction to really test for any air escaping!

Maybe It's a case like the Mack with a turbine housing too large,but Piers said that his compressor side is more efficient than stock and therefore I could go up one housing size without losing any boost pressure or spool-up time. Still have my 12cm housing,but isn't it a bit too restrictive as far as back pressure is concerned? There is a lot of talk about these 16cm non-wastegated housings for more exhaust flow. If I close off the wastegate on my 14,I can drive the turbo up to 46psi(way to damn much I know). What do you guys think?How about smaller injectors instead of those 370 marines?

 

[Extreme1]

If the turbo was the only change, you should see lower EGT's and a little more boost. With the fueling you're running, the change from a 12 to 14 housing isn't going to be very noticable as far as boost goes. The wastgat might be stuck open. Call them, they'll help you diagnose it, great group at PDR.

 

[Deezul1]

After installing my PDR HX 35 my mileage increased while towing but is the same when empty and I have the 16cm housing. It also slowed the EGT rise and cleaned up the smoke quite a bit. My TT is only 6500lbs so not near as heavy as you tow. Sure sounds like something is wrong other than a bad turbo.