Hello,

I know a good bit about turbos and MPFI , but not much to do with TBI systems....


We just acquired a 1990 D150 with a 318 TBI engine, and of course, it is weak, but low miles (75K), so I told my dad we should look at a single or small twin turbos for it....



He really wants to do the underhung turbos because of the ease of mounting underneath the truck, and although it is not ideal for lots of power, we might be able to reach our goals sufficiently by doing the underhung setup...


I told him that I think a max boost should be around 7-8 psi, and it should make a great difference in power, of course, with the correct turbo(s) picked out....




The biggest questions I have are:

1. Should I upgrade to a 1990 5.9L Ecu and throttle body and match the manifold for the larger venturis?

2. I am thinking a 255LPH high pressure fuel pump is what I want to use...... am I wrong?

3. FMU ? Why or why not with the TBI setup? what Ratio to start with to be safe and get leaner as we tune it in?

4. Does anyone program these ECU's for these trucks at all? I used to play with turbododges, and these are the same basic kind of computer, so I would think someone could tune one for a boost ignition curve using a 2 bar map sensor maybe?




Thanks in advance!

RYNO

 

Blow through carb or magasquirt. Those TBI injectors won't cut it at all. Blow though carb is by far the easiest and cheapest. You can go with a conventional ignition system with MSD.

 

+1 on the throwing the TPI away.

 

Dang, I was honestly really hoping to be able to keep the TBI system for reliability and simplicity (and good drivability in all weather conditions)......


ok, I understand the points of going with a Blow through Carburetor, but, what could I do to make this work with TBI?

Couldn't we mod the fuel injectors for more flow or swap on a 360 throttle body and computer?


even running them at 70psi of fuel pressure wouldn't be enough to allow the extra fuel required to push 7-8psi of boost safely?

That seems hard to believe.....

 

I think that the injectors are held down by plastic caps with orings aren't they? I doubt they would stand much more than the 14psi they run at. If you put a 360 setup on it will be over fueling all the time. Say good bye to drivability. You can be the guinea pig if you like though.

 

hahaha...... ok ok... i get it.....



well, with an oxygen sensorin closed loop, it should be able to turn down the injector pulsewidth at part throttle and negate the larger injector and venturi sizes..........



I definetely need to just take this stuff apart and see "IF" I can improve it and make it work sucessfully....

 

Yes it will trim it down to a degree. How much on those early computers I don't know. The later JTEC will trim to a maximum of 33% but keeps that negative adaptive when at WOT. So it still needs a way to fuel under boost. In comes the FMU I the big thing that I am not sure of is if the injectors will handle the added pressure of a FMU... I have never seen a TBI used in forced induction. What holds the injectors down and seals them in place? I remember it being a very weak looking plastic cap with a thin oring. It has been years since I have even had the air cleaner off of one of those. Duner has played with lots of magnums maybe he has played with the TBIs???

 

hmmmm......

I wish I could find someone versed in tuning these kinds of ecu's.... I wonder if someone capable of tuning the turbo dodges of these years could do that.....


I know a lot about those old 2.2 and 2.5L turbododges.....


if the issue is retaining the injector caps under high fuel pressure, I should be able to make a hold down clip or something nice and functional to work with that....



Duner is one sharp cookie, I used to really enjoy seeing his 4.7L stuff when I had a 2002 dakota before it got totalled... :-(

 

Jeremy Formatto is the TBI guy for Chebbys . Call and talk to him , but I'm sure he will tell you they will just not support any kind of HP .

http://www.fasterproms.net/




Blow-thru ...............

 

If you attempt to program this computer, you will have no simplicity, and if you do not, you will have no reliability. A standalone, or even a carb, would give you more of what you are looking for.

 

Ditto on what everyone else is saying. That era of Dodge TBI stuff is just about the worst foundation to build a turbo setup on. I have not seen anyone yet on the webboards I frequent that had any good info for how to performance-tweak one of them.

Turbo setups aren't cheap, and AF tuning is critical. Your system will be even more expensive if you use that TBI and ECM (you'll either damage an engine or have to install better stuff down the road anyway). Remember - 'penny smart, nickel foolish'...