Alright so I have a Cressida with a 7mge that the previous owner was in the process of putting a turbo on. My first question is can I use a boost modulated fuel pressure regulator or do I need to convert the ecu? I believe it has the 7mge ecu and wiring harness. Second question, will there be any difference for the vacuum lines or can I order a kit for the mge and be okay? I know the wastegate will need a vacuum line but other than that, it should be fine I think. The pistons are stock but the rings are gapped .020 over stock gap so compression will be lower. Should I do the right thing and install lower compression pistons or just leave it how it is and install the vacuum lines and stock wiring harness?
Picture 1 is where the oil lines go into the block. The rest should be pretty self explanatory. I have an oil cooler and intercooler ready for installation but I don’t want to get ahead of myself.
Whoa nelly....
Bottom line up front - I'd take off all that turbo stuff and focus on getting it back up and running as a stock 7M-GE before you bother with literally anything else.
Digging in - Lots going on here:
First, every FPR with a vacuum reference is boost modulated, in that vacuum/boost reference will change the base fuel pressure. But what I think you're talking about a Rising Rate FPR, or a 'Fuel Management Unit' (FMU), -different brands called them different things- which were hackjob back-in-the-day solutions to add more fuel to an EFI car with a bolt on turbo. Typically these were advertised with a ratio like '3:1' or '5:1' meaning that every 1psi of manifold pressure would raise base fuel pressure by 3psi, or 5psi respectively.
Fuel pumps back in the day struggled with those sorts of pressures, starting with a ~35-45psi base pressure and adding 35psi more fuel pressure to max at 70-80psi fuel pressure when you were at 7psi of boost.. logging fuel pressure would show pressure all over the place and it'd likely still be too rich or too lean and you'd regularly fry stuff.
With modern high pressure capable fuel pumps, and if you were willing to leave it alone at 5-6psi or so.... it might kinda work for awhile. I'd never recommend it though.
Not even sure where you'd find one that wasn't some $40 chinese piece of crap that you shouldn't trust with the life of your engine.
So, hard pass on any kind of fuel pressure fuckery devices. Stick to a 'normal' ratio (1:1) AFPR as sold by a quality vendor like Radium, Fuellab, etc. Aeromotive is OK but I've had issues with Aeromotive FPR's leaking vacuum and other weirdness in the past so I'd buy a Radium or Fuellab instead.
7M-GE ECU and wiring harness - okay, now can you hypothetically put a turbo into this and it'll run? Yep. But the injectors are way too small and the ECU and AFM don't have anywhere near the range to make this work well. Are there dicey workarounds that worked back in the day? Yes. Would I ever recommend them in a world with $1500 standalones like the ECUMaster Black? Absolutely not. Believe me, I have lived the broke car guy life most of my life, and I'd have been a lot less broke if I just saved up the money for the right answer instead of always trying to go cheap, buy used parts, and cut corners.
Honestly, given the 7M-GTE ECU's problems and reliability issues, I wouldn't even recommend hunting those parts down and bothering with any of that. You're just trading one set of problems for another. Save up the money and go standalone with a proper crank sensor, coil on plug ignition, and modern EV14 based injectors, and live happily ever after. I noticed the clutch master cyl so doing a standalone setup is pretty straightforward since you're not messing with auto trans controls.
But I'd definitely get the car up and running with a stock 7M-GE setup first so you can sort out everything else in the car like the driveline/brakes/suspesion/etc and just enjoy it as is while you save up to do a proper turbo setup.
Rings gapped .020 wider than stock - my dude, this does not reduce static compression, this simply increases how much blowby you'll have past your rings. Going wider on ring gaps for big boost builds on really rowdy engines is a thing, but it is absolutely not a thing with an NA-T 7M-GE on stock pistons, and I'd never ever go that wide on additional gap.
It'll run as-is but you'll be down on power, add lag, reduce MPG, and fill catch cans a lot faster for any given HP level you're at for the life of that engine.
If you have the means and space and tools, I'd pull that engine right now, pull the pistons, and reinstall new Hastings or similar rings to the factory ring gaps found in the TSRM:
If you wanted to reduce or increase static compression, you need to change the volume of the combustion chamber when the piston is at top dead center (TDC). This involves a thicker headgasket or pistons with more dish volume, like the 7M-GTE pistons. Personally on 7M's I prefer the Wiseco pistons that are around 9.0:1 especially if you're going to run a standalone.
