I have a 93 D250 4 speed auto (with 18 cm turbine housing). I want to start making some improvements to increase the power for towing. I intend to start with a full set of gages, Tach, Boost, Tranny Temp & EGT. After reading these forums, I believe I can get about an extra 50-60 bhp by tweaking the pump, and without trashing the transmission. I would appreciate comments on whether I am right in thinking this, from both the bhp and the trashing of the transmission point of view, but also particularly what pump settings to ask for.

I went out to two Diesel Performance shops, and got conflicting answers and prices.

One of the shops said they thought what I was asking for was reasonable, and gave me what I thought was a good quote. The second shop said they would also recommend a 12 cm housing. They said this would increase air flow at WOT and keep the EGTs down. They were also 3 times more expensive.

I question this, I thought the 12 cm housing would help spool up, but would choke the engine at WOT. Am I right in this or would it really help.

Has anyone seen such a wide spread in quotes for work? Now I don't know whether the cheap guy is too cheap, or the expensive guy is ripping me off.

Confused as usual.
John H

 

I wouldn't do the 12 cm housing since you tow. It really is restrictive at high RPM, which will raise your EGT's and hurt your fuel economy when towing. It's fun in traffic with an empty truck, but I think the 16 cm housing is a much better towing setup, and the 18 cm isn't really bad, it's just a little too big. The 16 cm makes more boost and allows you to add more fuel without becoming a restriction. I think the trans will survive pump tweaks if it's in good shape. For info on the pump tweaks click on the "tech facts" button, lots of info in there. You can do it yourself cheaper and you'll have a better idea of what's going on.

 

If you run the stock injectors and just tweek the pump the 12 cm housing is just fine. I had the fuel pump maxxed out on the '93 I had with a 12 cm housing and upper RPM "Choking" was not an issue. With the right tweeks to the AFC spring tension, you can tune the pump to give you good economy at towing speed and load. I had it set to a peak boost of 28 Psi, stock was around 14.

The increase of 50-60 Hp is easily attainable just with pump mods and is actually conservative depending on the pump tweeks you want to endure.

I was towing a 27' enclosed trailer loaded and I rarely took it out of 5th gear.

If you run aftermarket injectors then I would default to the 14 or 16 cm housing.

J-eh

 

I could do it myself, but I spend too much time on the road, and I value the time I'm at home. For some strange reason, my wife has this same philosophy.

I'm also at the stage where my willingness to do things, and my ability to climb around the engine compartment are not always compatible.

How do you tell if the transmission is in good shape? This transmission slips so much compared to the other gas engined vehicles I have, that I don't know how to tell.

I change the transmission fluid every 10,000 miles, including flushing the converter, and there is no burnt smell or blackening of the fluid. But I still have no idea if a band is slipping or not. Or whether it is one of those that goes first.

John H