will raiseing compression on the 7m-gte give me problems? what must i do?

[SUPRASTEVE]

Compression. Well the plan is to bore my 7M-GTE .40 over and make the head be able to have a 2.0mm thick head gasket... I found it it raises the compression. I also know that turbo engines have lower compression because the turbo is like a compressor and when boost hits compression raises. My dilemma is I think by doing what I want will raise compression so much that I might break something... My question is can I do all this without hurting the engine.... Actually I have no idea what I am saying I need some help.
Heres links to what i want is there anything else I need to make this work?

Head Gasket
http://www.suprasport.com/HKS-MHG-7M_p_261-96.html
Pistons
http://www.suprasport.com/CP-Pistons-0040-over_p_63-767.html
Cam Gears
http://www.suprasport.com/AEM-True-Time-Cam-Gears_p_63-324.html
valve springs
http://www.suprasport.com/Dual-Spring-Valve-Springs_p_63-768.html
Of course i will get stronger rods(stock length) and probaly a stock stronger crankshaft because mine is worn out.
Stage 2 cams
http://www.jscspeed.com/mk3/engine/bc_cams.htm

I have an idea on what will work for exhuast and turbo and injectors and fuel pump and AFM and intercooler.

yeah I know its alot of stuff you are probably going to ask dude what the heck do you even have the money for it. I say if you have nothing nice to say please don't say it. Negative comments suck but If you can help me with the knowledge I would very much appreciate it. I would like to make some new friends here and not enemies. Thank you so much!

 

[Doward]

a 2.0mm head gasket will DROP compression, unless there is quite a bit milled on hte head/deck.

The stocker is 1.37mm

 

[fool'ssupra]

Raising the static compression ratio is going to lower the point at which detonation occurs, other things being equal. You're not raising it very much, but the turbo is, as you said, going to add dynamic compression. The timing will consequently need to be retarded a bit unless you're planning on cooling the air/fuel mix. What are you planning on doing with the car when it's done?

 

[SySt]

What the guys said above is true. However, you also increase your chances of detonation by increaseing your quench distance (Piston to head distance), a thicker head gasket will do that. I'm sure most anyone here would say go with the thick gasket and don't worry about quench distance.

That said, the more compression the better as long as you can fight off detonation. The more compression, the higher cylinder pressure for the same given air/fuel mixture. Higher compression means you don't have to run as much timing advance which is also usually good. I guess I would recommend just putting the thicker head gasket in unless you're prepared to calculate everything else.

 

[SUPRASTEVE]

Hmm so how about if I go 1.5mm Thick on the head, that would be better. Also I do not know anything about the temp on air/fuel mixture totally drawing blanks LOL. Hmm what is better for the 7m-gte colder or hotter and how do i make it colder or hotter?

 

[SUPRASTEVE]

scratch that I will just put in a better head gasket stock size and go 75 foot pounds on it. hmmm I need more knowledge I can't wait till I go to school. I know some stuff but theres so much more to learn. I love it!

 

[SUPRASTEVE]

a 2.0mm head gasket will DROP compression, unless there is quite a bit milled on hte head/deck.

The stocker is 1.37mm

I see, now that I read what it did hahaha whoops. However the stocker is 1.37 I don't understand how the 1mm Hks Stopper headgasket lowers compression. I think that would be the best choice for me.

 

[Doward]

Wider bore area. Find out how much has been removed from your head and block, and calculate the needed head gasket. Try to keep your quench as tight as possible

 

[SUPRASTEVE]

Wider bore area. Find out how much has been removed from your head and block, and calculate the needed head gasket. Try to keep your quench as tight as possible

Ahhh... That explains alot I will find out from the previous owner of my supra.
By the way what do you mean wider bore area LOL. I don't know what that means, I am a noob. wider bore area for what the piston? the valves? =/

 

[SUPRASTEVE]

Raising the static compression ratio is going to lower the point at which detonation occurs, other things being equal. You're not raising it very much, but the turbo is, as you said, going to add dynamic compression. The timing will consequently need to be retarded a bit unless you're planning on cooling the air/fuel mix. What are you planning on doing with the car when it's done?

I am planning to make this car somewhat a daily driver and track car possibly drift car too. Its going to be an all around car. . How do I cool the air/fuel mix?

 

[zurud]

running rich or water/alcohol injection.

 

[SUPRASTEVE]

Well theres no way i am going alcohole so I guess running on the richer side won't hurt. There goes my MPG, LOL! It's a Supra who cares about MPG!

 

[Jack]

You will be better off with the Fidanza cam gears. We have had customers tell us the AEM slip under power. The AEM use 3 bolts to keep tight, the Fidanza use 5.

 

[hvyman]

the 1.2mm hg raises compression. the smaller the hg the more compression depending on how much material was taken from the head and block

 

[Koenigturbo]

Maybe this will help: How about port,polish your heads and a three angle valve job?? Maybe that will help, depending how you've raised your compression. By the time the turbo kicks in your gonna need that extra flow anyway. Maybe that will compensate for your higher compression

Chance's are I don't know what I'm talking about. Just a thought. What do I know, I'm noober.

That's what I did to my 7m, with the same gasket (1.2) I don't have any issue's,...yet.

 

[shaeff]

Maybe this will help: How about port,polish your heads and a three angle valve job?? Maybe that will help, depending how you've raised your compression. By the time the turbo kicks in your gonna need that extra flow anyway. Maybe that will compensate for your higher compression

Chance's are I don't know what I'm talking about. Just a thought. What do I know, I'm noober.

That's what I did to my 7m, with the same gasket (1.2) I don't have any issue's,...yet.

Uh, raising compression makes the turbo spool faster. Besides, using the term "kick in" in relation to turbo's is misleading. Compensating for high compression should be done with tuning. Yes, port/polish/3 angle job will help, but the key factor here is the tune.

Making the car run rich on purpose is bad, as you increase the risk of cylinder wash. Guess what that's a contributing factor to? Yep, rodknock. (fuel seeps past rings, thins out the oil, thus reducing it's lubricity)

 

[CTsupra]

One thing that you will need to do with a high compression + boosted 7m motor is to ALWAYS run race fuel.

 

[4U2QUIK]

Wouldn't raising compression increse low rpm torque, along with quicker spooling?

 

[CTsupra]

Wouldn't raising compression increse low rpm torque, along with quicker spooling?

you got it.

 

[Adjuster]

Half a point of compression one way or the other from "stock" at 8.5 is not going to cause the engine to blow up on pump premium, or feel so lazy off boost that you will not want to drive the car.

It can however, make the engine feel more powerful off boost if you are closer to 9:1 than 8:1, and it can make it more prone to ping, or have knock if your numbers are the same way as well. (IE: You must run the better fuel all the time to avoid it.)

My pistons are 9:1 by design, but the headgasket is a 3mm version from Greddy, and both the block and had have been machined a few times.. SO actually I have no exact idea what the compression ratio is on this motor.. LOL

What I do know is this. Forged pistons on the 7M tend to slap when cold, especially if you set them to 6k clearance. This is only made worse by pistons that are coated. (They do not expand as much is all I can figure.) Slap is no fun, but it does go away when the engine is warmed up. The ROSS pistons I've used seem to slap quite a bit when cold. Wiesco ones with a longer skirt design are rumored to slap less...

If you are going to build up a motor, I'd reccomend the following.

1) Pauter rods.
2) Wiesco pistons. Coat them with thermal barrier on the crown, and molydisulfied on the skirts with a thermal dispersant on the underside.
3) Bearings of your choice.
4) Get some 1mm OS valves. (They sell them on Ebay, and the stainless ones there are fine, I use them.) Have your valve seats cut for the new valves, and then blend the exhaust runners. There are many sharp edges, and they cost you flow/power. Don't waste time porting the intake, just smooth the rough/sharp edges, and it's plenty. Same goes for the exhaust.. Leave the port slightly smaller than the exhaust manifold.. That lip helps to give you better tourqe at low engine speeds.
5) Comp Cams Valve springs. They are about 70.00 shipped to your door, and they work fine with stock RPM. Your stock retainers and locks are fine. Spend your money on pistons, rods and coatings v/s valve springs, retainers and locks. The 7M is not a rev happy engine, so the stock rpm limits are what you want to build for.
6) Unless your crank is screwed up, do not have it cut. Use the factory bearings for the mains if you can. If not, make sure your machine shop goes for the tight end of the clearance allowed. It pays off later with higher oil pressure, and longer life of the motor. This holds true for all machine work on the 7M. Tight end of the clearance is the right way to go. Loose is not better on this engine, unless your talking about the piston ring gap.. LOL Then slightly wider is better IMHO.
7) Get an Asin/Toyota oil pump. Then take it apart, and check the clearance. You might find some machine work debris in there.. Clean it out, and then pack the gears with assy. lube, and re-assemble it. Get ARZ's cross over oil line upgrade. The fittings flow better than stock, and it's less hassle than making up your own lines like I've done. Carefuly remove the pressure valve on the pump, and shim the spring with one 10mm nut. Just slip in in between the spring the piston.. This will raise your oil pressure to a higher value, and keep your engine happy for years to come. (The nut is about 5mm thick, and has a hole in the middle, so no problems there.)
9) Continue with the oil system upgrade by either going with an adapter plate, or tapping/plugging your block. (Search for it.) This will take your oil away from the motor, through a remote filter, then to a cooler and back to your motor. No more extra cooler bypass to bleed off even more oil pressure. The stock oil cooler makes a great power steering cooler.. You will need a larger oil cooler, and thermostat to make it right.
10)Stock cams are fine unless your going for ultimate power.. Save your money for a Maft Pro, bigger turbo, larger injectors and exhaust. It will make you much more power per dollar than cams any day of the week at this point.

Good luck.

PS: Stock the TCCS ECU is rich on boost, and uses the stock O2 sensor to trim/adjust fuel needs at idle and mid range. Only when your foot is fully into the throttle does the TCCS go really rich, and on a turbo car, that rich fuel tune is safe. (It cools the engine down.) Around town, and while just driving along off boost, the TCCS is going to try and keep the engine close to 14.7:1 as possible, so your fuel economy will remain fine if your O2 sensor is working like it should.

There is quite a bit of information on this subject.. Just search.