Has anyone made this change?

[jonlabree]

I am in the process of changing the Fuel Injection unit on my 90 Reatta to the tuned port version from a 91. Has anyone done this before? And are there any major problems that I can look forward to?

I have one concern that I can see. I am at a loss as to what to do about the

EGR Valve. I can not see on the 91 and the 90 has one that is electronically controlled. ANY help would be appreciated....

JON...

[Guest Greg Ross]

So what parts have you got?

You'll need the Snakes Inlet plenum and Dome, '91 3800 heads to fit the intake and exhaust headers to fit the heads. Bonus is the stock exhaust system will line up.

The '91 Exhaust outlet for the EGR should come off the front header, an American .25 coin makes a perfect plug using the existing nut fitting off the '91 EGr flex tubing. At the intake cut the other end off the EGR flex tubing leaving about an inch of lenght. Napa or the like carry rubber caps and plug seals for automotive applications. Find one to fit and slap a hose clamp on it. The stock EGR Valve, just find an out-of-the-way place to plug it into the harness and stash it away. It can happily clatter away on signal from the ECM and you should not have to give it another thought!

Oh, and then there's heater inlet and outlet tubing that may interfere with existing accessory stuff, bracketing etc.

[Guest MauiWowee]

Is the ECM different also?

[Guest Greg Ross]

I believe I'm correct that the '91 would have larger fuel Injectors. As long as you stay normally aspirated the existing ECM would work quite well. Program charts for Fuel/ Air/ Timing are no doubt a bit different between the two generations but, with a larger injector, and "Block Learn" the ECM will learn the effect of the the larger fuel supply/ larger MAF based on Oxygen Sensor values. The ECM will adjust Injector pulse width to suit rich/ lean condition. What it cannot adjust is the MAF. It will respond with compensation until it maxes out gm/sec. Air volume. This would happen before WOT but the midrange response after several days of learning should be quite an improvement.

Hal/ Padgett, I think this is the straight forward logic.

The one input that changed drastically in 1991 was the style of the EGR Valve. pre-'91 it is a triple stage valve/ three separate solinoids allowing whatever permiatations 3 different sized vale openings could handle. After '91 the voltage signal changed to a proportional range to manage a proportioning valve/ more voltage/ more valve opening. The EGR recycles exhaust gas back into the intake to dilute the intake charge. If you don't have to do a "Smog Test" you'd be fine. What I was suggesting above was with the '88-'90 ECM programming unchanged you should be fine to simply plug the '91 EGR plumbing openings in the Header and the Intake, and simply stow the old EGR valve anywhere in the engine compartment, plugged into the wiring harness connector and forget it. It will give the circuit feedback the ECM looks for and will clatter away merrily doing absolutely nothing. No ECM fault codes would be set.

I could probably be charged under your EPA regs for recommending such a thing but the Smog Police would have to come and get me!

[padgett]

The interesting thing is that our '92 TranSport 3800 ("L" engine with snakes) apparently has no EGR (must have been an exemption for light trucks). Was really surprised when I could not find one on the engine or mention in the service manual.

[bwarren]

I am yet to find an EGR valve on my 91 as well as flex tubing or ports on exhaust manifolds. I pointed this out to others while at Bob Popyks in New York this past July. We were all stumped. I still have not looked in the service manual to see if it is mentioned. The EGR is not mentioned on the emmisions routing map/sticker that is attached to the strut tower either.

[harry yarnell]

That's because it doesn't have one. There were a number of 3800's in the generals stable in that time frame that didn't have EGR's. Don't know why.