SlingShotRX7

I have a T78 with all supporting mods.

Whats the highest boost I can run on 93 octane pump gas??
IM currently set for 15psi. Was wondering if I could maybe
push it up to 20psi safely, on pump gas..

thanks

moehler

iTrader: (12)

You might be able to run that much boost with water/alcohol injection... but if that system were to run out of fluid or fail... watch out! .

You can also look into low compression rotors...

With a stock rotor FD engine and no water injection, it's not possible to do safely.

SlingShotRX7

Even if its tuned good with solid AFR's??

Asleep

Not true. You comment should have started our with "I don't think its safe." And then you could have added "If it's tuned for it."

I've done it, it can be done, if you don't know for sure use "I guess" or "I think" or "others say and I'll parrot!"

Tony

Asleep

If it's tuned for it. You answered your own question. So what is it that you're asking?

GoodfellaFD3S

iTrader: (213)

17 is my personal limit, and that is on 94 octane.

You can have the best tuning in the world and (in my opinion, happy tony? lol) at 20 psi you are cruisin' for a bruisin'.

slingshot, i recommend you call a few shops and ask.....steve at gotham, chris or ari at rotary performance. They will *not* recommend 20 psi on pump.

moehler

iTrader: (12)

LOL... ok, I'll reword it.

"I don't think it's safe" .

Just because people do run 20 psi with no WI and high comp rotors, and I am aware that people do it, it doesn't make it a great idea. And it certainy dosn't mean that it's "Safe".

Asleep

Happy!

Of course I'll add that I log every mile I put on the car.

I would not run 20psi as a daily level of boost unless you knew how to tune it.

Tony

Maxthe7man

Correct... I run 20 psi as my daily boost level and 23 psi as my high boost, and sometimes only on 91 octane gas with premix.
No water injection, and no magic pixie dust.

ErnieT

iTrader: (2)

With our motors already being a ticking time bomb, I would not take chances over 15-16psi on pump without some sort of meth/water inj., to drop the intake charge temps.

dhahlen

iTrader: (5)

I ran 24psi on a T78 on 91... did about 40 hard runs before she blew. I dunno how she lasted that long =)

But I should have stayed at 15psi all day.

Thats as high as I would go now.

RICE RACING

20psi on pump only is a walk in the park, you need to find a specialist who has experience in doing this

28psi on pump with WI is a no brainer, ^ same as above.

15 to 17psi is for pussies who dont know how to tune, or want a over excessive saftey margin to cover their **** :P

Above is not form a text book or of the net, its from running multiple cars this way for many years and all make ridiculous power day in day out for 1000's of miles

RICE RACING

WI is the key to stoping apex seal errosion on leading edges *biggest problem* following the deadly detonation bug most struggle with when trying to run proper boost levels.

Same can be achieved (at a lower level though) with fuel dumping *running rich*, heavier pre mix, and appropriate spark timing values ........ all result in more powerfull engine that is more durable at the same time.

Sure you can make more power tuning leaner and meaner but you can end up with an expensive pile of junk real quick too, which is all to common. Find someone in your area who has experience and a proven record setting up rotaries at these higher power levels and let them work their magic. On the street life begins at 20psi

ErnieT

iTrader: (2)

Where the hell you been Rice? Hiding under a rock? Havn't seen you for months!

RICE RACING

Hi

Busy working on my FD and doing other random jobs

crispeed

I second that!

pistonsuk

Are you a specialist? If so, are you or any other specialist willing to share these key parameters that make these boost levels sustainable on pump gas?

Timing? Split? AFR?

Justin

Asleep

No.

If someone did then as soon as you blew your engine you'd be crying about lack of mothers milk. Okay, maybe not YOU, but some other you.

Besides most of "IT" is out there. Test it, apply some logic, get to some difficult questions and someone will share enough to keep you moving.

books

iTrader: (8)

Asleep and Rice;

I attempted to raise my boost from 15psi to 16.5psi in an effort to incrementally increase the boost up to 17-18psi range. This was performed on the dyno. I am logging EGTs as well as AFRs.

The IGT and IGL timing was changed 1 degree at a time for each dyno run.
i.e. the entire boost row was changes a degree at a time.
I tested timing changes from an IGL of 6 degrees at 5,200 rpms up to 12 degrees at 5,200 rpms.
The trailing timing was adjusted in step with the leading to maintain a 14 degree split.

The results were not promising and I did not attempt to raise the boost any higher.
The horsepower at 16.5 psi with less advanced timing was about the same as the horsepower reading at 15psi. The AFRs were approximately the same and the EGTs for the higher boost were about 40 degrees F higher. I don't recall any significant changes in knock.

Any insight would be appreciated.

Rice, you mentioned premix is that in addition to the omp?

Asleep

What computer, Haltech?
What kind of plugs?
What kind of port on what block?
What were AFR's at when you say they stayed the same?
Where is your torque peak?
Did you dyno it at 12 IGL (after torque peak) and 16.5psi?

books

iTrader: (8)

PFC
9's
stock port
approx 11.0:1
peak torque is close to 5200
I did not raise IGL up to 12 on all runs...I'll revisit the maps...most likely if IGL was 6 at 5,200 then Igl was probably at 11 at 7,200

of course that was with the map with the lowest IGL (6 degree) for peak torque

Asleep

Pm'ed

t-von

iTrader: (8)

I know that rotarys are less detonation resistant compared to piston engines. I was reading an article of the new 911 twin turbo. That car is going to be running 22+ psi on pump gas. Why is it that the piston engine in that car can run that psi on pump safely on a dailey bases, while our rotarys would easily go kaboom?

Asleep

You are comparing a new car to a design and ECU over 12 years old? I'd don't even think we need to go into the basics of design of the engines when the brains alone you're talking about are signficantly different.

Take a step back and compare apples to apples and ask why is that the boost level on the same make of car can now support more psi?

Step farther back and consider the design changes from the first turbo Porsche and the impact an intercooler had in subsequent years.

Things evolve (to some degree even most would agree).

In 1993 what production turbocharged piston engined cars were there and what boost levels did they require for the octane rating?

t-von

iTrader: (8)

You have some good points, but that still doesn't explain why a rotary can't enjoy 20+ psi boost levels as the piston engine can at 93 octaine. Sure the tech involved in the new Porche is new and advanced but, we rotary guys also have access to the new turbo/ecu technology that's far more superior and efficiant than 12-13 years ago. I'm not trying the compare stock for stock to make for an apple to oranges comparison. The facts are the piston Porche is able to safely run that 22+psi on 93 octaine but any rotary (new or old) would have a serious problems doing the same safely. I'm just trying to figure why?