|Re: other 7mgte stuff :)
|| 2003-09-28 20:54:00 <Jonathan Walker>
Ok factory internals on a 7M have been known to get around 500hp (in USA) at
the wheels IF the head is torqued correctly.
500hp is very optimistic on a correctly torqued factory headgasket. If you aim for 500+, you do the work - METAL headgasket.
Maximum boost depends on flow/fuel cut. People call the this boost cut but
this is NOT correct. It does not really have much to do with boost as it
runs off flow. There is a BIG difference!!
Boost cut/fuel cut = same thing. People have different terms for different stuff. Your fuel will cut when the ecu can no longer reliably fuel the engine at a given level of boost. This will be very close to the maximum flow rate of your fuel injectors. Fuel cut is triggered when fuel flow approaches the maximum possible flow rate.
Some days you will find 10PSI
will get you flow/fuel cut where-as other days you may find 15PSI is
capable. Its all due to the ambiant air temperature at the time which will
cause the air mass to be denser on a cold day and on a hotter day the
opposite where the air is "thinner".
Simply caused by above, mass air pressure higher in cold temperatures due to relative density, blah blah blah.
From my knowledge the flow/fuel cut works on when the AFM flap is pushed
fully (or close to) open and hits a micro switch activating the cut. The air
FLOWING past the AFM is what makes the AFM flap move not boost as there is
no boost at the atmosphere side of the turbo.
I believe fuel cut is triggered by the ecu based on sensor calculations - I know it's not triggered by AFM aperature.
Piggy back??.....*bang* (shoots suze in foot) DONT SAY THAT EVER AGAIN!!!
Reason I'm so mean is due to my theory above.....if the AFM is maxed out the
ECU is not going to be aware of any more air going into the engine and
therefore not going to provide any more fuel which in time will lean out and
then BANG (your engine this time not my gun ;-)
You can piggy back your ECU to defeat the fuel cut, but only do this if you have provided a means for the EFI to fuel above the factory specifications. Failing to do so will result in a boost past your fuel cut and possible max flow, and serious detonation as soon as the engine runs insufficiently rich. This will either kill, or damage severely, the engine. Depending on what you're aiming for, you can either start again with the EFI using an aftermarket configurable ECU and LOTS of dyno time, or you can set your sights within reason and carry out the reg reimer lexus afm/550cc injector mod. Not sure exactly what boos you can run with this, but I hear it's sufficient.
How close am I to the truth, anyone? ;-)
From: "Suze *Spite Me*" <firstname.lastname@example.org>
> what is the actual maximum boost i can run on factory internals (nevermind
> the turbo i'm replacing with a big booty :P) so with turbo out of mind
It doesn't sound like you've done an incredible amount of research on the subject...when you say big booty what do you mean? How much do you plan to get out of the engine? Have you studied flow maps and nutted out what you REALLY want to do with the engine? It's no good coming along and saying "I want to work the snot out of my 7M how do I beef it up?' when no one has any idea where you want to go. If you wanted to take it out and race group A styles everyone would say 'stainless oversized valves/forged pistons/nasty cams/crower rods/beefcake crank/motec efi' and if you just wanted something to smoke little boys at the lights I'd say leave everything standard, make sure youre motor is tight, and lexus afm and injector it with something a little sexier than a c26.
> can i run
> Also what is the factory overall compression like 8.9.2 type thing, ahh u
> know what i'm talking bout even if i don't lol
Once again, no point arguing about lowering compression if we don't know what you want to do with the engine. Do you plan to run 30PSI of boost? if so, start saving.
> is boost cut and fuel cut the same thing or are they separate annoying
> quirks? has anyone piggy backed their 7mgte and successfully gotten rid of
> them, also any consequences for piggy backs?
The CT26 will start to max out at around 14-15psi so anything above that you
are going to strain the turbo without much gain at all, or you will get gain
but the turbo will have to work 10times hard to got from 15-17psi as it
would from 10-12psi
If she's thinking lowering compression, if for the right reason, then the ct26 will be on the junkpile.
If the turbo is reco'd and prehaps upgraded to T04 compressor wheel etc you
should be looking at around 15 for the MAX power to strain ratio.
Same comment about the junk pile applies - aT04 wheel aint working even a minute amount of mucus out of it.
Altho I wouldn't recommend running standard i/c and intake pipes if your
going to run higher boost. There's no point running 15PSI when your intake
pipes etc are not flowing as much as they could or should. Imagine if it's
15psi at the engine what it is at the turbo, 18, 19 20, 21,22?????
Standard 1G piping loss of 2PSI at 15PSI. 7M piping I imagine will be even better. Once again, if she's thinking of running *excessive* boost new intake pipes and chargecooler go without saying.