Some of you may remember this car. It's an 85 GT that used to belong to Predator, on this forum. Way back in the day, a friend of mine bought it from him. He drove it for a while, but it has been sitting for... ever. It's currently sitting in my garage, waiting to be looked at. (As soon as I get the keys from him - long story - and replace the battery.) The current owner said he thought it had a bad map sensor. But who knows?
So... The background. 85 GT. 4 speed. Miller Woods stage II setup. I think it has an intercooler, based upon Predator's and Travis's (remember him?) old posts, here. It supposedly has the 85 ECM, with a "tuned" chip, and a knock sensor. It also supposedly has a piggyback tuner, called a "dyno-tuner", or some such. Trouble is, I seem to remember that it has a volatile memory, that obviously is now blank, due to the dead battery.
Obviously, technology has improved by quantum leaps, since the car was built. What is the hot ticket for a "mildly turboed" 2.8. I don't want to compromise reliability for that last bit of power.
If the car already has the Miller-Woods PROM, shouldn't it run as-is without the piggyback?
From memory, the Miller-Woods kit didn't require the use of larger fuel injectors; it just opened the stock Fiero ones to 100% duty when a lot of fuel was needed.
So, are you looking to have normal-sized injectors, and possibly a new computer to control everything?
If the car already has the Miller-Woods PROM, shouldn't it run as-is without the piggyback?
From memory, the Miller-Woods kit didn't require the use of larger fuel injectors; it just opened the stock Fiero ones to 100% duty when a lot of fuel was needed.
So, are you looking to have normal-sized injectors, and possibly a new computer to control everything?
That's what I was wondering. But there were some problems. It's blown at least one set of head gaskets due to running lean. Apparently that lean condition was also observed during the dyno runs. (Maybe that's what the "piggyback" was about.) (A search of "Predator" in the forum and archives was a real eye-opener.) I'm not sure if that was due to a poor tune, or too small injectors, or just the injectors being clogged. I never read that they were replaced.
I'm thinking about replacing the injectors with something that won't have to run 100%. The car dynoed 190-something at the wheels. That's ~210-220 at the crank. IMHO, 15s just aren't large enough. I had 19s in my 3.4, to accomplish what should have been about the same power.
I'm also not against swapping ECMs, if there's something more suitable. If there is a suitable tune already available for the original ECM, given a known set of parameters that I can meet, I don't have any problem with that, either. I'm sure that there are more than a few people out there who have experience with this kit. Lots of "institutional knowledge" as it were. So...
[This message has been edited by Raydar (edited 12-04-2023).]
I can't add much but maybe you can talk to Shem on here and make a deal with him on his injectors. He mentions the "beefy injectors" in this thread. He bought an 88 that came with the Miller-Woods setup but it was already removed from the car. https://www.fiero.nl/forum/Forum1/HTML/100415.html
[This message has been edited by IMSA GT (edited 12-04-2023).]
Thanks guys. Much appreciated. Can't do much of anything yet. Waiting for the keys to show up. (They rolled it onto the trailer in a hurry, and left the keys.)
Originally posted by Raydar: If there is a suitable tune already available for the original ECM, given a known set of parameters that I can meet,
Probably the first logical step once you get the car running is to evaluate the mechanical state of the engine. Compression, valve opening, vacuum gauge readings, check spark plugs, etc.
If you're not sure of the engine's mechanical health, then you don't have a set of known parameters.
[This message has been edited by pmbrunelle (edited 12-04-2023).]
I love threads like this. I remember the Miller Woods when I still had my original 85 GT. But there were life changes on going at the time. Go get 'em!
Probably the first logical step once you get the car running is to evaluate the mechanical state of the engine. Compression, valve opening, vacuum gauge readings, check spark plugs, etc.
If you're not sure of the engine's mechanical health, then you don't have a set of known parameters.
Thanks for that. That's good advice. In the absence of ticking or clattering, it's easy to assume that everything is good, when it may not be. The owner was not be aware of anything major, but I'll check, anyway. It probably hasn't run in almost ten years. I'm sure it will wake up "mad".
Obviously the gas in the tank will be "shot". Probably the pump and injectors, too. At this point, I'll be happy if the tank isn't all rusted up.
[This message has been edited by Raydar (edited 12-04-2023).]
For injectors, if you know what the crank HP is, injector size can be calculated by the number of cylinders and the duty cycle. Several injector sources I spoke with don't recommend more than an 85% duty cycle.
At 190 HP, 6 cylinders, Gasoline, Turbo, 80% duty cycle, you would need 24 Lb injectors or for 220 HP, would require 27 Lb injectors.
[This message has been edited by fierofool (edited 12-04-2023).]
At 190 HP, 6 cylinders, Gasoline, Turbo, 80% duty cycle, you would need 24 Lb injectors or for 220 HP, would require 27 Lb injectors.
That's interesting. At ~210 HP, 19s were plenty for my 3.4. (I forget where I got the formula from, but it never ran lean.) Of course, the rules may be different for a turbo. Thanks. (Maybe it was based upon the 80% duty cycle.)
That's interesting. At ~210 HP, 19s were plenty for my 3.4. (I forget where I got the formula from, but it never ran lean.) Of course, the rules may be different for a turbo. Thanks. (Maybe it was based upon the 80% duty cycle.)
The "reading" continues...
Hi Radar, just piggy-backing on some of the thoughts of others here... I'd agree that getting it running first is probably the most important thing, just to make sure it actually runs.
My advice would be to go with an aftermarket ECM... just my thought. MicroSquirt has a whole new harness and support for all the things. I have one of those which I will eventually put on my daughter's car, after we've restored the car, just to make sure it's running well with the stock ECM, etc.
There is not really a duty cycle percentage limit as such; it is more that you must leave enough time in the cycle for the injector to fully close, and then reopen. I think that 2 milliseconds of not spraying fuel is enough for this.
So, acceptable duty cycle depends on RPM, and the number of injections per 4-stroke cycle. The Fiero ECM (and other batch-fire alternatives) for instance opens the injectors twice per 4-stroke cycle, so there's a bunch of time that's spent opening and closing the injector; you should account for this.
I may have a set of 30 lb/hr injectors I can send you, but I have to look in my stash to see if I still have them (I can only look on the weekend):
Patrick, Thanks very much for the offer. It's very much appreciated. Before you go and dig those out, let me figure out what I'm doing. Those are exactly twice the size of the stockers, so they might be a bit of overkill.
