Maximum Boost with T78

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Hi Guys,

Im not sure how much boost i can run safely with my set-up. I have a greddy t78 with pulleys, ignition amp, FC, complete hp fuel system, IC, etc.. Basically i have everything except for porting and 3mm seals. What do you think the highest boost pressure I can run. I have a boost controller so adjusting it wont really be a problem.


Thanks,

Chris

 

what size injectors and what pump flow/psi? my estimate is 20-22psi. if you had 1600s and 850s. with a high flow pump

 

I have 1600sec 1000 prim. walbro pump, 500++ hp capable. The thing is i ONLY have 2mm Apex seals and stock ports.

 

the seals and porting shouldn't make much difference on maximum boost, but the porting could take away from some of the higher rpm power. i've got a similar setup with a different fuel pump. i know for sure i can get 21psi out of it, but i'm going to see if i can tune for 26psi soon

 

Stock Apex seals will shatter and crumble my motor and my turbo rotors if too much boost is used. A am looking into rebuilding the engine with a full race port and 3mm seals soon. But as of right now, I need to know how much boost can I safely run with 2mm seals. Thanks.

 

He answered your question.

What kind of gas will you be using?

 

wrong. that's a big misconception with these motors. many people have ran 30+psi on stock 2mm seals. 3mm seals do not aid in strengthening for boost. they are just there to aid in slight knock situations where 2mm seals may not be able to take it.

 

If you think about it, what's another 30psi in addition to the hundreds of pounds of pressure that are created in a normal combustion cycle? If fuel is properly mapped, stock 2mm seals will work just as well as 3mm seals. Actually more power is possible since there is less friction (that's if all other things are kept equal).

 

Good thread this as i too have a T78, nd will be winding up the PSI soon to around 18PSI max though!!!

 

Hmm... I'm having rotary power in gardena take care of the install and tuning. They told me that it isn't a good idea to push this motor because it is basically stock. I was told by them that the max psi i should run would be 13lb. I was so bummed because I thought I would be able to push a lot more and achieve higher hp. Oh well i guess I have to kick out another 5k and port, build, and 3mm my engine.


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Chris

 

Your problem/limiting factor is your fuel pump. That pump is good for ~400rwhp(~15 psi on a T78) with a rising rate FPR. Most guys use two of those pumps. The stock seals can handle whatever boost you can otherwise support. I have run 30 psi on stock seals without a problem. That said about 15 psi(400-450rwhp), and you will be running out of fuel IMHO.

 

I have 404rwhp right @ 15psi running a supra tt fuel pump, chris at RP told me Iam gonna need to run a dual pumps if I want to run any more boost to be safe.

Ps I have 1600cc's and FPR and rail as well.

 

Oh.. on the rx7 store.net website, they said that the walbro pump is good for 500 hp... The shop right now is telling me i can only run 13 psi... and i called rx7store.net and they told me to run 14 max... I am so confused right now. Btw do you guys know any good shops in so cal?

Thanks,

Chris

 

dude, don't spend that much money for a motor that you don't need. you'll gain at the most 30whp off of a street port on pump gas and a t78. use the motor you have and wait til it eventually goes to spend the extra money on a new one. unless your motor has like 100k miles and smokes, i wouldn't worry about it.

i have the denso competition pump that rx7store sells and it has done wonderful for me. i'm putting down 439whp at 16psi. it should be plenty enough for you

 

Drive your car first then think about what to do later. you havent drive 7 right.

with your set up you shuold got around 370-400WHP. that is a lot of power. and 400WHP RE will feel much faster than any 400WHP piston engine car

 

who told you that?! lets see... this year Dee makes (not finely tuned) just under 800hp on OEM 2mm seals on lower boost. when running gas last year and it was tuned, was making 770hp on the same motor.
shatter and crumble??? i better give him a call and tell him to watch out.

 

Diyman 25 thanks for the advice... I'll do that. I have driven the car before the major upgrades.. I get it back today. Supposedly only 13lb of boost.






A shop called rotary power told me that they wouldnt push the car.. I asked what they meant they said that you couldnt run high boost with it.

Chris

 

Ummmm... actually its multiplication. If your compression ratio is 8 to 1, then you are compressing the air that is at 14.7 psi atmospheric 8 times. When you compress the air in a turbo you are raising the pressure another 30 psi. That comes out to 44.7 psi absolute, then multiply that 8 times. Thats the difference between 118 psi and 358 psi.

edit: those are the pressures at tdc before combustion occurs.

 

on my HKS T04R motor, My hight BOOST mode is only 14 PSI. and I got about 400WHP. I knonw compare to some of fourm member's car my number is rather small. but I think this is more than enoght for my goal. and I build this car for Street and some Track day driving. so building a not reliable hight HP power is not my goal....

 

either they just want the extra money for installing a new motor or the problem is something that you're not telling us. how many miles are on the motor? have you done a compression check to see what condition it's in? they may have discovered that your motor isn't very healthy and needs to be replaced due to that, not because it can't handle boost. a stock mazda remanufactured 13b-rew with nothing done to it, can take well over 30psi

 

6000 miles on motor, properly broken in, and no compression loss. they said, " the 2mm apex seals cannot handle such a high boost pressure, 3mm is much harder to break." Rx7store.net said, " I recommend only pushing 14 psi max." So i dont know.. these rotary shops seem to give the same answer. It is not a rebuild motor either, it is a brand new crate motor.

 

experience proves that 2mm seals are just as capable under boost as 3mm seals.

rx7store told you 14psi max due to your fuel pump. if you go any higher, you will starve the car for fuel and it will definately not last.

there are a ton of threads on here that will get you more familiar with your car, please do some searching

 

on the rx7store website... my pump is supposedly rated to 500 hp.

 

which with proper tuning on a t78, would be about the amount of horsepower at the flywheel that you would be making. most accessories like that are rated for flywheel horsepower, not wheel horsepower

 

This guy must be the most stubborn uninformed member I've seen. Listen to those that have done it, the apex seals are not limiting your boost.

I'm running 19+ psi on 2mm apex seals and could run much more if race fuel was only $2/gal and available at the corner Chevron store.