V8TT Supra Project Diary

[KazeSupra]

Kaze, just a comment along the lines of Justen's. Even with the engine's requirement for more E85 than normal gasoline, you may find the 1600's are tough to get a good idle with.

It's a bit like putting a 90mm butterfly on a 2 litre motor and trying to use it to control the idle - it just ain't gonna happen. That's why we have IAC's.

Seems manufacturers are solving this situation with two sets of small injectors rather than a single set of big ones, since the big ones just don't turn down well enough.

If your ECU has some spare injector outputs, you might think about setting up a primary/secondary injector arrangement, using 550's or 750's as your primaries to get a nice idle, and then put 2-4 big ones at the manifold and batch fire them as secondaries only when needed at high load. This arrangement might also work better for you if you get "stuck" somewhere and have to use regular pump gas.

Also, if you're going to go ahead with those 1600's and they happen to be P&H (low impedance) injectors, make sure your ECU can drive them natively, ie with a true Peak & Hold driver arrangement - none of this rinky-dink stuff with a resistor box. If your ECU doesn't have true P&H drivers, then you really need to consider getting one of the aftermarket P&H boxes like the AEM. Otherwise the ECU's saturated drivers just aren't going to have the initial "umph" to bang those big puppies open fast enough.

I actually think it won't be that tough to use the 1600s to idle.. There's a video of a Supra (from WOTM if anyone follows what goes on at Supraforums) with an AEM and 1600cc injectors and 280 cams that idles pretty well at 1100rpm. They run on C16 and lower compression then I will, but I don't think it will have that much of an effect as most people think. I'll do a search to see if I can find it.

I have considered using dual injectors. In fact, the ECU that I was initially going with has additional modules where I would be able to add from 8-10 additional injectors that I would have come on when in boost. The only problem with this is...waste spark. I don't really care for it, so i'd rather get an ECU with 8 injector and ignition drivers. So now I've been looking at other ECUs that have those requirements, and all of the one's I'm deciding about can utilize either low or high impedance injectors natively.

Thank you for the constructive discussion, Gentlemen.

 

[cribbj]

It's true that the AEM has some features to get big shooters to idle better and people have been successful doing it. There's a function called microsec/bit which can be optimised in a nonlinear way so there is much more resolution to fire the injectors at the low end.

There's also an injector voltage/response table that can be tailored for each manufacturer's injectors which helps smooth things out.

Whether the other ECU's you mentioned have these features? Dunno.....

 

[KazeSupra]

Finally a project update...I got the heads off of it, as well as most of everything that's on the engine. Only Major items I have left are:

Crank pulley
Oil pan
main caps
crank.

Then I'll finish disassembly and cleaning and go from there.

I've been playing around with different setups and I can't quite put my finger on a setup that I want. I was even playing around with a sleeved block, but Justen talked me into staying 4.0L.

I'm still trying to find an EMS with 8 ignition outputs and 12-16 injector outputs. I'm trying to find something that would run 8 * 750cc injectors all the time and then bring in a couple of 850 or 1000cc injectors once boost comes in. I can find a few that can do one without the other, less going with a Motec. *sigh*

Anywho, this will probably be my last update for a while unless someone has questions. I start back to school on Monday, so anything I get done will be God's will only.

Thanks for looking.

Chris.

 

[4000GT]

Must be going by now?

 

[UZZ-TT]

Do you have the Supra shell? hmm I was really hoping this project was going somewhere.

 

[4000GT]

Any updates mate?

 

[Jake Breyck]

his last post on this forum was almost exacly a year ago.