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Discussion Starter · #1 ·
Yes, I've searched a TON.

Ok, bit of background here...

I have a 89 NA Supra, that we put the turbo motor in.. Motor was from an 89 with the gray plug ecu, the ecu and the wiring harness also.. Now.. With the wiring harness.. the BODY plugs under the glove box were different, I had to repin those wires.. but I used diagrams and have had no "body" related issues.

The first motor I put in, had bad machine work done to it.. So it smoked like crazy with a brand new CT26 turbo on it.. Took it apart, had a cracked head.. Put a new head on it, still smoked, rings were terrible.

This time, I had a motor sitting for my 88 Targa car.. So I got tired of waiting and I threw it into the car.. Complete with a GT4088 turbo and 4" stainless exhaust all the way back and an HKS knockoff external wastegate. (FunkeyMunkeys) old setup.

Engine was freshly rebuilt with brand new rods/oem pistons/bearings.
Stock head
ARP head studs
ARP rod bolts
ARP flywheel bolts
Titan Motorsports 1.2mm MHG

The car runs fine, and seems to be normal except it has VERY little low end power.. and the turbo doesn't run above 0psi until 4k rpm.

Now, (I expect to hear some, "DUMBASS" here..) I am running stock 440cc injectors because I was wanting to break the motor in before the 750's came..

I've done a compression test and had no issues.. result were:

#1 - 165
#2 - 180
#3 - 165
#4 - 180
#5 - 170
#6 - 180

Timing was checked, rechecked, and rechecked again, because that's what it kinda feels like to me..

I drove the car a ton when it was NA, seemed to have more low end power.. but have never driven the Gte stock, So I may just be expecting crazy power even without boost.. But it seems weird to me..

MBC is all the way down, assuming the wastegate spring would let the turbo build the 8 or 10psi.. But I'm also not driving the car past say 4200 rpms...(break in)

I have an LC-1 wideband in the car with an XD-16 gauge to monitor the A/F and also have the LMA-3 on the way so I can datalog and at least tune for now with an SAFC Neo (flashed to the right firmware for karman to work right..)

The A/F when im WOT is between 10.8 and 13.0 roughly (No actual datalogging yet)
A/F at idle is normally higher than the 14.7 ideal.. Around 16-19, when it hits 19+ it'll bog and run weird, but go back to 16.5ish (Scary).

I have an Aeromotive AFPR kit installed and I have the base pressure set at 40 with the vac off.

My main question is.. should the car feel kinda sluggish? Not sure if it's just the big turbo not spooling at all under 4200 rpms, or if it's a fuel problem.. (20 year old injectors?)

If you have to call me a moron to fix it, that's fine.. just trying to drive my car again lol..

Thanks a ton

Also, redid the entire injector wiring harness from the ECU to the injectors, then to the resistor.. Just to make sure it wasn't a 20 year old brittle wiring issue.. 750cc injectors will be here and installed Tuesday also..

Super Moderator
11,529 Posts
Nobody goes to the MK3 technical section anymore - that's not your fault, but if I'd seen this post sooner I would have responded. As it is, I only saw this because it was the top post when I viewed the forum index.

You basically wrote a wall of text when you should have simply said you have a 'freshened up' stock motor with compression numbers on the verge of being outside of spec, while running a stock ECU, stock injectors, and a (relative for the setup) huge turbo.

Do you know how much material was removed from the block surface and cylinder head deck to prepare for the MHG? What made you pick a 1.2mm?

The bottom line is yes, the GTE will feel a lot more sluggish in lower RPM's than the GE because it's surrendering over 1 1/2 points of compression, and the turbo itself is an exhaust restriction, particularly outside of boost. I don't know why you picked a GT4088, but suffice to say that I've never seen a GT4088 setup on a 7M-GTE or a 2JZ that impressed me - they are always far laggier than their mediocre power output justifies.

If you want, and you're planning to stick to lower boost levels and/or slightly richer a/f's (11.0:1 or so in boost) You can bump your base timing advance on the CAS up to about 13-14* BTDC and that will help overall response considerably, but it's also putting 3-4* more timing in at peak torque so you have to run fatter to help prevent detonation.

For your intermittent A/F issues, particularly at idle, tells me you've got a post-MAF intake leak somewhere. If it's only the A/F that's affected I would look between the MAF and the Throttlebody, if the idle speed is also bouncing around a bit, I would start at the intake manifold past the throttlebody. Don't forget to test your whole system, and double check your accordion hose at the same time.
The DSM-style boost leak tester made from a suitably-sized PVC pipe end clamped into place at the turbo inlet with a schrader valve fitted so you can use an air compressor or tire pump to pressurize the whole intake tract. A spray bottle full of soapy water also helps too.

While you were in the engine, I'd have gone .020 over and installed some forged pistons and ARP rod bolts at the very least, particularly if you were interested in running a larger turbo. The stock pistons have held to much higher power levels, yes, but that is with a standalone and hardly any timing advance - even just a few detonation events in boost at that level would break the stock piston ring lands almost instantly.

I know what your answer is - you didn't want to spend the money. I'm sorry if this sounds harsh, but the 7M is not an engine to build if you can't spend the money. If you were simply interested in getting her freshened up and back on the road with a CT upgrade, exhaust, IC and an LS400 MAF and 550's, that'd be just fine. But once you're going to a tubular manifold and bigger T4 you should be building the engine and hopefully budgeting for a standalone as well.

Your choice in piggybacks is just... confusing. A single Zietronix ZT-2 setup would do everything the XD-16 and LMA-3 do and then some, all in one self-contained unit too. I would ditch the LMA-3 ASAP and get on board with a better engine management setup, preferably a standalone.

And while your compression numbers are supposedly 'in spec' according to Toyota, I'd be very concerned with them for a fresh motor. Are the rings seated yet? Have you done a compression test with a teaspoon of oil in each cyl to see if it's a ring issue? On fresh engines, everything is suspect, and your variance in compression numbers could easily be a fault in the valve job, or just the result of a tired old cylinder head with beat up valve seats.

As for Supramania, I don't know where to begin with that place. When I think of Supramania I can't help but envision a bunch of underemployed neckbeards and skinny CS majors arguing over the stock 7M-GTE ECU's timing table while one of them builds an MS-II on a workbench under a carport in his overgrown backyard.
People talk about egos being big here on SF, but SM is much more xenophobic and harsh to newbies, and feelings are quick to get hurt over there.

Good luck with your build.

84 Posts
Supramania gets stuff settled! no bullshit form anyone saying anything they think is correct. why would we want newbs always posting stuff they dont know about? Ya they do get prett yharsh over there though. lol

Supramania is ALOT better for 7m related stuff and Supraforums is better for JZ stuff. To each their own.
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