RotaryEvolution

iTrader: (30)

so this engine i built about 8 years ago, has had a few rear irons replaced but it's finally starting to die. last time i compression tested it it only had about 75 psi after the rather harsh 70k miles i've put on it since it was built(the engine now has approximately 150k-207k miles on it with mixed used parts). it's been through many trials and experiments over the years as i learned the limits it could take and patched it together. as well as the above, it developed an internal seal leak about a year and a half ago after it sat parked in the garage for a year, learning that the RA/Mcmasterr carr coolant seals aren't all they're cracked up to be even though they are reusable.. the leak has sealed up for the last 10k miles after driving the car daily for a bit but i know it is borderline still and is pushing air into the system under hard pulls but it is still holding fine(not sucking coolant into the motor anymore or running warm).

alright, now that the meat has been said. i have been pushing about 350-375 to the wheels on the motor for the past 9 months at 14psi on the T70, the methanol injection system is half removed as i used some parts to finish a customers car, if i reinstall the pieces to push the car up to 20psi it should be pushing approximately 500 to the wheels, BUT the reliability aspect goes down per HP you add.

as it sits the car is 100% reliable making the power that it does and i drive it on long trips averaging 23mpg on the highway(it can do better, if i spend the time retuning the highway maps), i use it as a truck also delivering and picking up engines driving up to and more than 500 miles one way on some trips.

but i come to question why i have a car capable of over 500WHP that i limit for the sake of reliability? i trick myself by telling myself that it is reliable and gets better mileage than any of our other cars but something inside wants to see what will happen if i just do turn it into what it is, a weekend car and push it's limits.

so, should i leave it be and enjoy what it still is or just say screw it and reinstall the methanol and see what it can do? my main concern is the rear iron breaking again under the stress. it is still just a S4 rear iron and they are hit and miss when pushing over 400 to the wheels with the small dowel pin boss that it has. pros, even if it does blow up i can build a more fresh higher compression rotor engine for it, i am hardly thrilled with the 8.5:1 rotors after all these years. i guess i just question why i build cars faster than my own but also i do like being able to jump in and not have the worry that i may need a tow truck on stand by just so i can burn off the tires as i slam the brakes to slow for traffic. if i do, i will also have to do a V-mount intercooler as opposed to the saab intercooler i have sitting in front of the radiator, this will help reduce pressure drop to get more HP per PSI and eliminate the possibility of the plastic end-tank FMIC from exploding at those boost/power levels..

i am only limited at 20psi in part because the microtech i bought back in '05 was a basic cookie cutter one with the stock 2.5 bar setup, which could be upgraded to 30psi later on. i also just worry in part because going past 17psi on pump fuel really puts you in the orange/red zone for the car doing what it does every day for years as it has so far. so, one more experiment for the 7? hmmm. even though it has 207k miles on it, i think it can handle it, i just rarely get to tap into the power that it currently has so i'm on the fence.

j9fd3s

iTrader: (3)

this is my problem too! in the bay area, you only need like 60hp... the 160hp NA is too fast most of the time....

a 500hp rx7 would either be WAY better (you'd be so fast, it would be like the waco kid), or totally useless

MadScience_7

As someone who has only had a chance to drive a 160hp NA (if that, altitude sucks), I think I would be perfectly happy with 350. Unless you have a second car for a DD, stick to reliable IMHO.

RotaryEvolution

iTrader: (30)

with that i guess i should elaborate, we have 5 cars between me and my gf. the '89 GXL is mainly our DD on days when we don't have to pick up the kid and on days when we do we have the mercedes turbo diesel and i will have my '74 REPU as work truck as soon as i get the title done on it, then the big truck will be sold(i never drive it because it gets 7-12mpg). then there's the duc for the nice days outside, so backup transport isn't an issue.

MadScience_7

Wow. That's quite the collection. In that case I can't think of a good reason not to make it a straight up fun car.

Derekcat

iTrader: (8)

If building another engine is no issue, then have fun ^_^
[Just don't get bitter with the 13B and start thinking LS-swaps are "the only way" lol...]

Also, have you run it with 500HP before? How did that feel? Is it worthwhile for everything else that could go wrong [half shafts, trans, etc..]?

TheAbsence

iTrader: (19)

Only boost it to 500hp if you're ok with the possibility of it blowing immediately. If you don't want it to blow right now, then don't do it.

RotaryEvolution

iTrader: (30)

building a new engine isn't really an issue, i have a a good S4 TII motor loosely assembled on the stand in the office as a display model, already cleaned and painted, just would need more work such as pinning and porting. so maybe a day and a half to build a spare motor.

part of the problem still, is finding time, which doesn't seem to be growing on trees as i work my *** off for half a days pay these days.

NI_Racing

iTrader: (4)

I say let it run! you didnt spend the time and money to learn how to make it scream just to gag it for "bs" sakes. Fix the meth, boost 20 pounds, and see what she does. If it blows up, rebuild it. if you want a reliable grocery getter, then sell the 7 to someone who will exploit its sports car nature, and buy an srt4 (or some other bullshit "import") and do all the shopping/commuting that you can handle. Your car has been begging you to stretch its legs, and if that wasnt the case, you wouldnt be thinking about it let alone posting it on rx7club. Free your car! turn it loose! post pics!

SirCygnus

iTrader: (1)

Blow it the **** up!

Turblown

iTrader: (12)

Recently a s4 t2 engine was brought to us with a cracked front iron, we replaced the iron during the rebuild. It is now at 23psi; no cracked irons so far... Its all in the tune/setup...

beefhole

iTrader: (29)

You only live once. With back up vehicles, go crazy with the engine. 500HP, why the **** not? If you have the opportunity (and spare funds), take it.

-Crash-

^Couldn't have said it better!

clokker

iTrader: (2)

I'd think the way to approach this would be to ask what will the extra 100+ HP actually do for you.
It's not just engine reliability and fuel efficiency that will suffer but the entire drivetrain- from the clutch to the tires- will be stressed as well.

It's funny...the other day I followed a Veyron (I see TWO of 'em fairly regularly!) down University boulevard- speed limit 40mph, normal actual speed 45-50mph- and it struck me that his 1000HP/million dollar supercar had absolutely no advantage over my asthmatic NA in this particular real world scenario.
In fact, outside of a racetrack, I'd say my bang-per-buck enjoyment ratio is probably better than his.
How often, and where does he get to exercise his thoroughbred?

Probably not a popular viewpoint but maybe one to consider.

RotaryEvolution

iTrader: (30)

this is one of the main ones i consider everytime i think about just doing it for the sake of doing it, for every full throttle run there is hundreds of miles of traffic and hours/days between. another 100hp would put me more out on the highway versus generally fun all around, i don't want just a dyno queen and it is plenty quick as it sits now so i just don't want to do it just to put up a dyno sheet that i could have done years ago. hell, the T70 collected dust for almost 2 years before i even installed it onto the car when all it too was making an oil drain pipe and modified downpipe to up the potential horsepower from 325 to 550ish.

BUT what i think i will do as a compromise is finally set it up and tune it to 20 and install a switch for high/low boost, too bad i dont have the 4 bar on the old microtech or i could do a real experiment and see whether the T70 can actually do it's rated 600WHP.

-Crash-

This maybe true for the Veyron, even if he did drive the Veyron like it was meant to be driven it would still be expected of that car because it's, well, a Veyron for cry'n out loud, but when you have something like an FC but putting down 500+ HP, most no one expects that, ESPECIALLY the cops lol.

I say put the meth parts back in, make a second high boost map, then have your cake and eat it too.

DeMoe Aurelius

iTrader: (4)

You know Rebel sale 100 octane out there!!! I'm not sure what part of Vegas your in but there kind of spread out I know I've gotten Race gas out there when my boy came down before I moved back to Cali. Thats unless they stopped sellin it. I think the one on Tropicana I for got what street its on. But going east from like Decatur on the south east corner. Thats only if your worried about octane. Do what the car was designed to do run it, have fun, you only live once and your car can ALWAYS BE REBUILT. Unless its wrapped around a phone pole and we know how slippery Vegas streets are so Boost carefully but mainly on the freeway !!!

RotaryEvolution

iTrader: (30)

that station doesn't sell 100 octane anymore. i know the station you're talking about because it's 2 city blocks from my shop. race gas isn't difficult to find but i plan on doing it on pump gas, which has been done plenty already. driving on race gas off the track is far too expensive.

ineedfc

iTrader: (3)

turn it up, track it until it blows. then consider it a fun learning experience and you know what a 500hp fc can do.

Spirit-RE

iTrader: (25)

Do it.

RotaryEvolution

iTrader: (30)

i stand corrected, compression tested the engine and it was at 90psi hot compression with a weak battery, so the engine actually built compression again since the last test about 20k miles ago up from the 75psi with good cranking speeds i measured at that time.

AI is back in and fixed a few boost leaks, namely the HKS SSQV which was sticking half way open which i cranked down and disconnected(yes, i'm now running no BOV). still builds boost slowly with the blackstone saab IC core so that is next to go before i crank up the boost, which as of now is sitting around 15psi with the 10lb spring in the WG.

for now i'm just running straight water through the AI to get it out of it's 2 year dormancy, as there's also only one place to get methanol here that i have found.

on a side note, surprising about the compression figures i did run this engine for a total of about 1k miles without any premix or OMP after doing the last compression test which i do believe helped lap the seals lap back in and raise the engine's compression which does rule out the myth that a rotary engine will fail within 1k miles of running no seal lubrication or fuel cut on decel hurting your engine. the 90psi compression figure is average for a low compression CR S4 TII engine with ~150k mile rotor housings which have about 40k miles of hard abuse on them. i still wouldn't recommend not running a seal lubricant though, i'm sure the seals did take a bit of wear during that lapping process(atkins soft seals, 2mm still pushing ~350WHP after 75k miles on this engine).

swapping out the smaller mid-mount IC core for a larger core v-mount should net some efficiency and bring in about another 20% more top end power and quicker turbo spooling. too bad i'll only be limited to about 20psi with the cookie cutter original LT8s with 2 1/2 BAR map sensor. also working on a boost controller for the microtech to help spool the turbo quicker once i set the MBC to 20 and a switch to put it on low boost, all without the need for switching to an EBC.

Len-Len

iTrader: (9)

Wise choice! There was no reason not to crank the power up IMO. Please make a vid of this ol' bastard when its done.

arghx

iTrader: (3)

Way to jump on my bandwagon

I really want to run 20psi for a while with no AI just to prove it can be done on 93 octane and 8.5:1 rotors. I've run FD's up to 18psi on the dyno with AI switched off, 93 octane.


also FYI I have never broke an iron, whether it's series 4 - 6. My old engine took many detonation events on its s4 irons. I switched to s5 irons because I got a good deal on them.

RotaryEvolution

iTrader: (30)

yea, i saw your thread and saw other people running no BOV so i figured it was worth a shot, aside from a little bit of surge at around the 10psi range it actually sounds like it's normally venting at higher boost levels with no surge.

i know it's possible to run 20psi on 93 but out here we can only get 91 octane which usually results in a broken rear iron. while i'm sure you may not have run into it yet, i can assure you i know very well where the limit of 91 octane is.

87octane= 9psi
89octane = 13psi
91octane= 18psi
reasoning dictates you should be able to go:
93octane= 22psi
E85 @~97 octane= ~30psi

you will be running very close to the detonation level at 20. internal combustion temps will skew figures up and down, if you have good intake temps you should be able to get by but for a track car that is spiking all temps i wouldn't suggest pushing the limit.