Boost Questions about 7M-GTE

[Fubar231]

I was wondering what i could safely crank the boost up too on a stock 7M-GTE engine. Also does anybody know of any boost kits or something that replaces parts and allows you to crank your boost way up. my friend bought a turbo mod ready kit or something for his audi and can safely crank it up to 22 lbs of boost on mostly stock engine. Does anybody know of anything like that for the 7m-gte supra? Its a 1989 Supra Turbo Auto. Thanks for anyone who can help.

[UNATUL APIRTED]

well depending on how many miles are one it...i still wouldn't even think bout tryin to push 22 pounds on stock internals and expect it to last very long. My roomate has an audi A4 and yeah he can push about 20 but his engine can handle it. Also if you haven't already herd about the terrible hg problems with the 7M. So i would suggest upgrading the internals before tryin to up to boost.

[Jeeves]

No, you cannot. Stock fuel system will support NO more than 12psi. If you try to pass that point, you'll run into a wonderful device called fuel cut. At this point the ECU will quit firing the ignitor and it'll feel like you've run into a brick wall. Literally. The car will jerk and stutter and feel like hell. So, for your safety, stay below 12psi.

Besides that, there's about 12 other bottlenecks in the stock system that will prevent or slow you down, in your case you've got the Auto which sucks power outta the car as well. On top of that, you're a stock block with a crappy stock headgasket. Those who up the boost without consideration for the rest of the system will quickly find themselves with a blown head gasket.

If you want a few extra psi without risking too much, go look up "shimming the wastegate".

Boost Kits? No such thing for our car. You can buy bigger turbos, and better intercoolers, and so on but when it comes down to it fuel cut-off will still be there. Stick to the known upgrade paths and such a thing won't be an issue.

[Fubar231]

Well right now my car runs i think 6.5 lbs of boost? I wanna crank it up to like 11 lbs, and what would be a better/stronger head gasket.

[Fubar231]

Okay so ive been looking around and i understand what to do. But not 100% on what to use. People keep talking about the mm's of there washers and some people say try 3 and then go from there, using 1 mm washers, some people say they got 8mm's on there and stuff. Mines entirely stuck except a exhaust. Its not even that great of one either. I wanna put it to about 10 lbs of boost and its at i think 6.5 I was gonna start with 3mm's of washers and then go from there. What do you think 3mm will do. And from what i understand with the stock turbo each lb of boost is 11 hp. so increasing 3.5 lbs would gimme roughly 36-37 hp for 50 cents?

[Jeeves]

Not really. Doesn't work that way. The 11hp thing is an OLD number and depends largely on mods to support it. Personally, I'd tell you not to go more than 10psi. The stock HG WILL go. It's only a matter of when.


Go search on the HG issue. It is not something you can simply replace.

[Fubar231]

Do you know of any diagrams or anything that i can look at cause im not entirely what to do. I understand it but not sure what to do. Thats the only problem. And what sized washers do i need?

[Fubar231]

Jeeves i dont really have a problem with replacing things on my car cause i got a entire shop w/ lifts and air tools. Things are pretty easy actually. So greddy offers MHG's for around 250$. I could get that, but what do you think an ETA on replacing a headgasket would be in a shop w/ air tools etc. Before i do this im going to get the ARP studs and bolts too. I will probably do this before shimming anything just incase. The MHG for 200 or so and ARP studs and bolts for 130 or around there isnt too bad. Plus giving my friend 100 or so for doing it. That'd be great if you could tell me how long it would take to replace the head gasket and what size i would need, what bore/thickness, and include replacing the studs and bolts in the time if you could.

[Fubar231]

I dont really have to worry about maching my block either i believe because the head gasket is not blown so it shouldnt be warped. Wich should save me some time in the whole process. If i bought a greddy MHG and arp studs and bolts what would i torque it down to? I hear some people say 72, and some say 74 to 75.

[Jeeves]

Originally Posted by Fubar231

I dont really have to worry about maching my block either i believe because the head gasket is not blown so it shouldnt be warped. Wich should save me some time in the whole process. If i bought a greddy MHG and arp studs and bolts what would i torque it down to? I hear some people say 72, and some say 74 to 75.

Ideally a greddy is a good gasket (but unless things have changed) there's usually a good 6wk backorder on them, if not greater. Warping has no effect on the requirement of machining the block, this is done because the surface must be a perfect mating surface for that new gasket. Slapping a MHG into a surface that's been mated to the stock composite gasket for >15 years is nothing but bad news. I've seen engines start and NEVER have the MHG seal because block/head prep work wasn't done. If you skip machining you can expect to have the HG leaking in under 500mi.

I've got ARP Studs at 85ft-lbs. ~72 was ths rating toyota changed to in like 1991 when HG's started failing.

[Fubar231]

So no matter what the blocks still going to have to be machined before i use the MHG?

[bgrieger]

It is the only way you will know that you won't be doing this again in a month or less. Some will tell you it held fine for them, but without having someone in the know inspect it, all the shadetree speculation and grass roots tests in the world won't be of much use. It's also cheap enough that if you're going to remove the block to inspect, you might just have it done for the insurance of it.

BTW, Toyota never increased the specs of the bolt torque in the TSRM. That has been a user found solution. Hence, you get hte 70-82 range often quoted. THink of 72 as a minimum acceptable, and perhaps 82 as the high end. Split the difference and I can't see it being a problem either. However, if you take the car to Toyota for a head gasket, they'll put it at 58 same as it left the facotry at.

[UNATUL APIRTED]

if you want to know if your block needs machining just get a straight edge and a set of feeler gauges and check the warpage on your block.. doesn't take more than a couple minutes to see if there is any warpage and you will know if you need the block machined. but like the others said...cant hurt to have it machined anyway but if your on a money or time budget just go the route of a straight edge and feeler gauges and see what ya find.

[Jeeves]

Originally Posted by UNATUL APIRTED

if you want to know if your block needs machining just get a straight edge and a set of feeler gauges and check the warpage on your block.. doesn't take more than a couple minutes to see if there is any warpage and you will know if you need the block machined. but like the others said...cant hurt to have it machined anyway but if your on a money or time budget just go the route of a straight edge and feeler gauges and see what ya find.

I've done that and have the blown head gasket to show for it. I will personally -never- recommend installing a MHG without machining.

[bgrieger]

That only tells you runout. What you need to see is much smaller distortions around the sealing surfaces and impressions from the fire rings on the old gasket. They're too small to measure properly with feelers, and a real machinist's squre that is itself flat enough to measure off of will cost more than the machine work.