Anonymous

Anyone on here know much about them?

Specifically in terms of whats required in the way of changes to get decent power from one.

Say someone was looking for around 600bhp @ flywheel, what would that typically involve?

At what point do they stop being cheap to tune to, like for example on a cossie YB i would say 400-450bhp is fairly cheap and easy but going much past that starts to get a little involved, whats the equivalent window in terms of the RX7 motor.

I believe they are fairly inefficient and hence need bigger turbos?
So a GT35R that might make 600-650bhp on a YB would only make 500 on a RX7 or something along those lines? Is that correct?

Any specific requirements in terms of turbo, like for example do they generally need a larger exhaust housing than a 4 banger or that sort of thing?



cheeRS

Stavros

Larger exhaust housing due to them creating much more exhaust gas than a piston engine.

600bhp? Well, providing the engine is in good nick, big single turbo conversion and the correct fueling and charge cooling should do it.

Id use GT40 size and a 1.05 ex housing for 600bhp rather than a GT35 i reckon.

And if the engine needs rebuilding, get it ported, but pretty sure they can do 600 on standard ports, tho bigger will certainly help.

(BTW i was considering doing a post saying uprated cams, big valve head, forged pistons, and so on, but cant be arsed, im off now for lunch )

Anonymous

PMSL @ uprated pistons etc


GT35 was just an example, its acutally a GT42R i was thinking of using, as i believe that you can get away with larger turbos on them due to the extra airflow so it still wouldnt be too laggy.

Stavros

GT42R would be huge, but HKS T51Rs are commonly used on them, and they are basically rebadged GT42s.

Ive been in two RX7s with T51Rs actually at brunters, and they drove just nice, lovely in fact.

Anonymous

Its just that i happen to have a spare GT42R knocking about, along with an AEM ecu that seems to work very well on a RX7 from what ive seen, so thought it might be a good excuse to use them both as ive always fancied an RX7.

Not just yet anyway, got too many other cars on the go, but just thinking about it now cause if not then it makes sense to sell the GT42R isntead as i cant think of anything else i would ever be likely to use it on.

matt p

Hi mate have you tried the mazda rotery club?

The site is very good for technical information

Ive been looking into rx-7's for a while now although
im only looking at basic mods from other peoples posts
on there it seems they just need a large turbo, big secondary
injectors 1300cc+, a V front mount intercooler and a good
ecu to run it to get to the power you are looking at. Also rx-7's
running single turbos sound amazing

A lot of the guys run the apexi power fc ecu with the commander unit.

Cheers matt

89xr2

Is it true that you don't need as much power from an rx7, say 400 bhp is very fast because of the way they make their power?

Anonymous

Ive registered for the site and had a bit of a look, but i thought here would be better to ask, lol

I would use the standalone management i already have as opposed to an FC

matt p

Would also be a good idea to upgrade the apex seals
and rotor tips when doing a rebuild if your aim is big
power. Otherwise you will be doing another rebuild
sooner that you would like

matt p

I see saves spending extra money then.

Some people opt for the HKS T04r its a little smaller but still
makes good gains to around 450-500bhp i dont know the
dimensions of the turbo but might be a little cheaper than the
bigger one as suggested above?

stonehavencossie

What sort of 0-60 etc would you get outta 400bhp rx7 ?

I thinks there are kool little cars and have always fancied one

Only problem is that i dont think there is any tuner etc. up here that can look after em :-(

xr4x4rs

iTrader: (5)

is it really that easy to get that sort of power out of them

ive always loved the rx7s but didnt think it would be quite that simple

if i knew that i would of bought one years ago and not bothered with all my other rs cars lol

theres a place in coventry that builds the engines just carnt remember the name

but ive heard about triple rotors? dont know how that works though

Anonymous

Ive heard of a RX7 with a similar turbo to mine (except bigger hotside housing) making 794@wheels

Its not really the right turbo for the job, but on the other hand, at 600bhp it would be so understressed it would fast forever!

matt p

Basicly its a sandwich plate that hold the two rotar houses together
so you just add another sandwich plate and an extra rotar this is very
expensive to do but they go like stink.

Carl hayward has built a quad rotar but at present its only an N/A engine
and when is running properly will be very devastating like some
of the aussie rotors

matt p

I see chip buy it once and never again then

794@atw That is going some!

Would be nice to see the progress of the car if you
ever do take the project on

Anonymous

Yeah, might give it a go once ive stripped the nova and sold the bits off it as i will have some more space then.

Stavros

And the most important and expensive bit....

A custom crank...

Cant just keep wanging rotors on top of rotors.

And triple rotors are simple as they are factory engines, the 20B engine from the Mazda Cosmo.

Well, technically Mazda did do a quad rotor, the 787B LeMans cars, but not likely to find one of them lumps, so gotta make your own.

I know Ross who owns Dragon Performance fairly well, and he not into 20Bs really purely as tuning them heavily involves doing a lot of custom stuff (managment etc), and when the 13B can be reliably made to wang out 800bhp+ and nice enough drivability with nothing too flash or complex, just off the shelf bits, he not fussed about 20Bs.

But id love a 20B personally.

xr4x4rs

iTrader: (5)

so is it just a case of

bigger turbo, intercooler, injectors ecu

or is there a lot more other bits aswell

Stavros

Big turbo/manifold/wastegate/exhaust/fuel system/intercooler/managment.

And a good tuner/mapper as even the ECU maps are very different to piston engine ones, and tuners not having a clue and fucking them up is part of what gives them a bad rep.

Anonymous

The 20B is in the higher tax bracket though

Anonymous

And a bog standard rebuild?

At what level are internal mods required?

xr4x4rs

iTrader: (5)

so not a lot then really

are they reliable at that sort of power

if the engine was in good nick

or would it be wise to have an engine rebuild

Stavros

Why rebuild unless its fucked?

But if your doing a rebuild youd be daft not to port the engine.

But im not so sure thickers apex seals/tips etc are a good thing, many people regard them as a bodge to disguise bad mapping.
They survive a few more dets, but wear the rotor housing faster.

Stavros

Oh, and...

www.diy-re.uk.com

Anonymous

If i were to extract 800bhp from a bog standard rebuilt RX7 but with it ported, what would break?

Would it sheer something? (like a 800bhp YB would snap the crank or rods in half)
would it wear out quickly? (i mean really quickly like so much blow by on the rotors they just die instantly more or less)
would it wear out quicker but be basically ok (like a 500bhp standard cossie engine dropped to 7.2:1 Cr)?

Anonymous

Will keep an eye out for it on limewire!

Stavros

Dropping the compression a bit is often a wise plan if talking big power.

But otherwise internally, whatya thinking of replacing? There nowt in there
Like said, its under some contention if harder/thicker rotor tips is a good or bad thing, and barring that, owt to it...

matt p

Its the same as anything really if its been thrashed and you
start turning up the power its not gonna last long

All depends on how deep your pockets are really dragon
do a drive in drive out rebuils for just over 3k more if you want
uprated seals/housings/tips etc.

The engine will last a while just get the compression
checked before you ever buy one.

But the rebuild will come round sooner that you would like

Anonymous

Wasnt sure on the crank, wether the main rotor itself would actually sheer off etc.

I actually really like the engine design, so would love to build one, but know nothing about it, obviously some things are similar to a 4 stroke, like CR requirements etc though.

What sort of RPM are they standard on the different models, and what can they handle if they are ported enough and have a big enough turbo before something breaks?

matt p

I see mate best ignore my last post then

Was not sure as ive seen people recommend them on the mazda site.

Anonymous

Indeed, i view the tips as probably being like Rings.

Try and get a load of power on an old set and they will give blow by and die.

Stavros

They can handle silly RPM, they almost perfectly balanced, you wont see a custom crank or rotors unless its a 26B or some non-production engine.

Revs isnt a problem, ever, thats a big bonus point of a rotor.

Heres a pic i took down Ross's a few weeks ago...

matt p

The redline is at 9k rpm but i would not like to try getting there
if ive just brought one well till i had it checked over

Have a look on the mazda site mate there is a guy doing a home rebuild
on his fd its got some really helpfull pics. Its under the 3rd gen rx-7 section was looking at it in my lunch break.

Also someone on there is sells a step by step guide dvd on rebuilding
the engine

Stavros

9k? Childs play.
Thats what they meant to do, stock late spec ones dont even chime the gearchange bell till 8.5k IIRC.
And when ive been in standard ones you didnt even realise you was at high revs unless you looked at the rev counter until the ding, ding, ding...

They dont need to be revved hugely higher, not until youve gone for the most obscenely huge ports ever, not in turbo form anyhow, let the turbos do the work.

xr4x4rs

iTrader: (5)

anyone got a link to this mazda site your on about lol

wouldnt mind having a look

im just downloading a promo vid see if it gives any clues aswell



im very tempted to get one of these cars in the summer now instead of another cosy

Anonymous

Thanks for all the info Steve.

Will buy you a beer if my new part time job ever actually drags me into the office at some point

Stavros

No prob, im no super expert, but know a fair bit, and driven and been in tons of modded ones (inc being driven like loons at brunters), so gives you some idea of what the deal is.

Dragons website--
www.dragonperformance.co.uk

ReWorx--
www.reworx.com

they the 2 UK tuners I trust anyhow.

Anonymous

Will probably ask you again in a couple of years when i get round to starting the project, so please try and learn more in the mean time if possible

xr4x4rs

iTrader: (5)

dragon peformance are they the people who had that purple rx7 with them gold blitz rims on

if so that was the car that made me want to get a rx7 one day just by the look of it

they dont do bad prices on full engine builds either

Stavros

Another reason I fancy an RX7 is they piss to work on in my opinion.

Well, once the twin turbo setup (which is massivley complex) is removed and converted to a big single.

The maze of solenoids and pipes involved with the twin setup is immense.

Luckily you can throw it all away once gone to a single.

I got Ross to show me it all when was down Dragon, piece of piss soon as you realise what it is.