bhp

[s.g]

hi people
 here is another question for you all, how much bhp can you run through a standard rx7 rotary engine. And also what uprated internals can you fit to withstand higher bhp(i know on standard engines you can uprate the pistons,cams etc but i am new to rotarys)

thanks
s.g

[iaint]

How long\'s a piece of string?

There are so many factors based on externals (mapping, i/c, etc) that will interact in a complex manner.  The stock engine (i.e. no porting or dowelling) will probably his a limit in flow (exhaust ports?) and upping the boost will bring diminishing returns.

You can push a stock engine to it\'s limits and it\'ll make great hp (with the right turbo and intercooler, water injection, etc.) but it won\'t last all that long.

That\'s why the guys running bigger power have varying levels of porting, ceramic seals, water injection and, in some higher boost applications, dowelling.

I\'m not sure that anyone here has pushed a completely stock engine to see how much they can wring out of it... it\'d last no time at all.

Iain

[gsb876]

Depends on if its twin / single turbo rx7 mate.

If yours is a twin turbo i think the most you can hope for is around 360bhp??? maybe someone running twin\'s should answer that.

Single turbos will run higher power but you may require the engine porting to do so, mine runs around 460bhp.

[bnaellis]

I should expect twins on a stock engine with boost cranked up a bit will run about 400fwhp.

rgds

[s.g]

cheers guys that has shed some light on the matter. i know about the porting but whats the dowelling (sorry if its spelt wrong) about.
cheers
s.g

[cruiser]

Without porting on stock fuel system you can expect up to 350fwhp. With porting and bigger fuel flow up to 400fwhp with record being around 450hp in the states.

When my turbos go, I will most likely go with the efini \'99 spec turbos. They flow better and have better spoolup and are good to around 400-450hp (can run up to 18psi, whereas stockers are usually only good for like 14-15psi).
Another option is a GT35/40 single :bandit

[Joel Kelly]

The last time I had my car on the rollers, I had uprated just about everything except the motor itself. I had a GT35/40, uprated fuelling, front mount, water injection, etc etc.

I made 312hp to the wheels (Dyno Dynamics dyno) at about 14lbs of boost. I tried more (up to about 14.5 psi) but power dropped away. My understanding is that this boost is about the limit for long term running reliability before you want to dowel the motor.

I seem to recall that Steve Cleary has since made about 335 atw(same dyno) with a slightly larger mid-pipe and an intake manifold with better flow characteristics (from a 13B RE?) on stock ports.

As for internal modifications for better power, I think most things have been mentioned already - porting, dowelling, stronger apex seals, stronger eccentric shaft etc etc.

Joel

[20B_boy]

More than 14psi on pump fuel leaves you with little margin for a crap tank full.

With the water setup right you should be able to pull more fuel out and/or add timing. Hopefully WI will take off on rotors here soon as it opens up a lot of possibilities for big power I think.

Steve made 335atw on a GT35, stock motor except it has an -RE centre plate, or may be -RE end plates? I think the former from recollection...

Any ways JK, how\'s yer big wing, king ding-a-ling?

[Joel Kelly]

Thanks for that Rich - I knew the exhaust ports were stock either way!

I\'ll try and get the WI up and running on the 5th July (when car is next on the rollers). To be honest, I want a sensible power/reliability compromise, so I\'ll get a safe map and then add the water to make it safer. I\'m not yet sure enough of the hardware to take fuel out etc in reliance on it.

As it is, 310bhpatw in these cars is f\'ing quick. God knows what 350 is like!

The wing just keeps on growing on me. I love it! I love the way it looks in my mirrors (which is lucky really - I can\'t see much else).

Hope everything\'s peachy in your World.

JK

P.S. Have you ordered the canards?

[maximtaylor]

Over 350 feels very ample

Max

Originally posted by Joel Kelly

As it is, 310bhpatw in these cars is f\'ing quick. God knows what 350 is like!

JK

[Ricco_04]

Why do you change a twin turbo arrangement for a single turbo.  I can guess from reading this that It gives you more power but I would have thought (at least before reading this) that you could squeeze more power using two turbos? :rolleyes:

[20B_boy]

Depends how big and what kind of setup your 2 turbos are really!

One big one with a well designed manifold and intake system is going to laugh cruely at the stock twins as far as making lots of power goes..

[FDDreamer]

Correct me if i\'m wrong, but i think that a single turbo set-up is also more reliable than the default twins, due to the complex nature of the twins, both in terms of the demands on the ECU (diff boost points etc i guess) and the wiring involved.

Seems as most people opt for a single turbo rather than replacing the twins with more twins, presumably because it offers more power and also increased reliability. Perhaps!

But i guess you could also make huge power from twins (as seen on several high bhp GT-Rs) but i\'m not sure if there is enough room up front for 2 big \'uns!?

[20B_boy]

The reliability problems with the stock twin turbo system come from the miles of vacuum hose and various solenoids which control them. After 10 years getting cooked in a very hot engine bay stuff gets brittle and cracks, starts leaking or breaks...

Non-sequential after market twin turbos are a different kettle of fish all together. Big power potential but complicated manifolding and hassle where it seems that for most applications one BIG single is more than adequate.

[FDDreamer]

Thanks Rich. Didn\'t know exactly the cause of the reliability issues but that cleared it up nicely!

But what is the difference between non-sequential twins and sequential ones? Would the 2 big ones function by simply coming on at the same time? Or one first, then both together? As standard, am i right in thinking the first one comes in circa 2000rpm, then the second one takes over at 5000rpm? Is only one \'working\' at once? Or at 5000rpm are both turbos singing? :confused: