Speed density - how far can you go?
 

First, some background, then I'll get to my questions:

A friend of mine has an 87 GT (SD) with about 60,000 miles on the clock. We gave the car (stock as stock gets) a complete tune-up and it ran very well. Great throttle response and clicked off a 14.8 on street tires. Not too bad.

Then, we installed a Hurst shifter, March pullies, BBK shorty headers (1 5/8"), 2.5" H-pipe, and 3 chamber Flowmaster exhaust. We took the car back to the track where it ran a little better with a 14.6 on street tires.

Next, we installed a Trick Flow intake. Once we started it, blackish blue smoke billowed from the pipes and the fumes just about knocked us down. The idle was very erratic - from 600 to 2000 uncontrollable. After checking and re-checking everything we pulled the intake and put the stocker back on. Bing-bang-boom all problems solved. Idles great, no rich exhaust.

So, will the SD experts give an analysis of what happened - and why this simple intake change (70TB too) caused so many problems? And, what really puzzles me, is why some folks here on the Boards run all kinds of mods with SD with no issues, while others can't change a sparkplug without having driveability problems. Is it some sort of computer issue, or a case of mis-matched parts? I'm very curious.

Note that the parts were chosen based on the owner's future plans for the car, which include TFS heads, cam, converting to mass-air, etc.

Thanks in advance for the replies.
E

I dont know whats wrong with your friends car.....I have a mildly ported GT-40 lower with Explorer upper intake, and E7's ported to the max and my car runs fine.

Try adjusting the TPS and the fuel pressure and maybe resetting the computer.

It makes no since to me that the car would smoke and blow out all those fumes just from an intake swap.

Im stumped,
Sorry...:confused:

Dark_5.0

Your car is a great example of the variances that I've seen. Some SD cars run with ported heads, different intakes, etc. and run great while others just don't. It's got me stumped too.

BTW - TPS was spot on.

E

I am waiting for my FPR to come in from summit....I finished my car last weekend I expected my car not to run right because its speed density.

To my surprised it fired right up and idled fine.

Just curious wich trick flow intake did you install?

I'm not really sure which version it was, nothing race oriented. I think it was the "street" intake setup.

E

Sounds to me like the MAP sensor was not connected properly, or you had an open vacuum line.

Disconnect the MAP sensor from it's vacuum line and fire the car up. Is that exactly the scenerio you had before?

I have the same combo as Dark_5.0, ported E7's and explorer with ported lower.
Before I swapped to mass air I had no drivability isssues whatsoever. It idled just like it did when it was completely stock.

I swapped to mass air because I plan on having a pretty stout combo down the line, and I found the meter cheap,so I did it.

It also sounds to me like a sensor wasn't hooked up or a vacuum line.

I Hope to get a Mid 12 out of mine maybe a low one with good tires I have stock SD in it.

I would suggest the conversion.

The wire harness costs about $25, the computer can go for another $100 and the meter can be from $30-200 depending on who makes it.

Cheers,

Thanks for the reponses.

Unit - yes, this is the same issue we had a long time ago. You have a good memory! :D I don't remember specifically checking the MAP sensor, but we went over all vacuum lines, connections, etc. and couldn't find a thing wrong.

E