For High Boost app on my 3 rotor. Should i Put s4 T2 8.5 compression rotors stamped D weight or should i just go with the 9.0 rotors that are already inside my 3 rotor. Remind you im going to be boosting at 30-33 psi. Whats the best way i should go (remind you also which ever rotors im going with i will have them lightend and balanced.

 

go with the 8.5:1 rotors, the people who hate on them usually have never driven a car with them. I find they hardly affect spool in a noticeable way. it'll give you some extra margin for error.

 

Yeah, with the 9:1 rotors, you're reaching the limit in at 15psi pump gas, 20psi AI or methanol. Severe detonations at those levels will likely dent the rotor.

Go with the 8.5's. They are much better casted.

 

But hp wise am i going to lose alot of hp if i go with 8.5.1 compaired to the 9.0.1? About how much HP im i going to lose give or take?

 

From what I know, no one found the limits of AI. 32+ PSI 700+RWHP....water injected, pump gas, no alcohol.... You should go with S4 NA rotors. Beefier casting than FD rotors and higher compression....

 

This is just "talk".. Where is the proof that the 0.5 makes that much differences? There is no such law that says "9:1 compression is only good for 15psi". thats horse ****. So many factors are involved here (not just a compression ratio).

 

exactly!

 

+1....I boosted a renesis to 16psi with a PT71GTQ and laid down 420whp on pump gas....on E85 I hit over 500whp at ~20psi on the same turbo....and the Reni is 10:1..its all about tuning...

 

Hold the phone guys... We have a WINNER! Someone knows wtf is up!!


Seriously, he's 100% bang on. Typically with higher compression an ignition map might be a bit more on the retarded side as where lower compression (typically) is advanced further. When you run higher octane fuel again, the ign is advanced.

so with very low compression and really high octane - you could expect to see an advanced ign map as where with really high compression and really low octane (think V8 NA) you could expect to see ign pulled back. ....or something along those lines.

 

the "horse ****" is your own interpretation, hwnd.

I was talking about difference in the construction of the rotor, and only in the case of severe detonation.

If you have the perfect tune in all conditions, then it probably doesn't matter. Otherwise, one bad detonation at 25psi with the 9.0 rotor could deform it. I know for a fact that most top PR drag racers all run the 8.5 rotors for this reason, and the OP wanted to run similar boost levels.

 

I might as well stick with the 8-5 since its better casting since im going to boost it high 30-35psi i have 8-5 on my 13B REW and was boosting at 25psi with a gt35r with meth injection and never leaned out i was still running rich. i have never had a motor with 9-0-1 compression so i never knew the difference on how it drove.

 

 

This is driving me crazy i wish there was someone on this forum or infact acouple people on this forum that has built 1,000 to 1,300 hp 3 rotor engines and acually have experience on whats the best rotor's to use for that application (minis the cast aluminum rotors they came out with since its real expensive)

 

well for starters, that .5 ratio isnt going to make a difference.

you will not be able to tell the torque increase of .5 ratio on these. if you were jumping from a 7.0 to a 9.0 then you probably could tell some "pick up" in the different rotors.

You are missing a major point here... here it is "there isn't a BEST rotor to use for XYZ HP".
Why not call MazdaTrix or Racing Beat and ask them? ...we're a bunch of stupid internet users. try a shop who has done it a time or two like Racing Beat.

Report back as to how the conversation went. Please mention your hp goal above.

 

Most people agreee to to use the 8.5 S4 turbo rotors.
I was concidering using 9.4 S4 N/A rotor and getting them lightened and port phased which would drop the compression ratio a little plus increase intake flow.
Carlos Lopez talked me out of it and said just go with the 8.5 turbos.

 

I never said you guys are a bunch of stupid internet users. I was just asking if anybody has any experience in high Hp engines. I found out from this thread that the 8-5-1 are stronger construction wise. And im asking these questions because i never ran 9-0-1 rotors in my entire life. I went from 1st gens to s4 2nd gens to a 3rd gen that had s4 rotors already in the motor with the rebuild and stayed with the s4 rotors. im just asking for knowledge. I understand that everyone has different experiences with different setups thats why i was asking.

 

i've read this before and i can't share any experiences with those rotors because i have yet to use them. however, what i do know is one bad detonation can take out far more than rotors - and oftentimes does - in which case whatever rotors you used are irrelevant. i think the point about state of tune versus static compression ratio illustrates this. bust up a couple of 20B housings in a detonation event and i'd dare say the prospect of replacing dented/crushed rotors quickly pales.

 

This was inconsequential until the last few years, when the likes of RA seals, ALS seals came on the market. Now ppl are cracking housings, denting rotors before the apex seals let go...

 

How? How could a seal not bend (at least those you mentioned) before an iron (several MM thick) cracks? Taking into consideration the strength of the apex seal (carbon, ceramic, steal, iron, wood, plastic, titanium, horse ****, etc) I highly doubt they could withstand as much force as the irons can.

Dude, I think you're full of it.

 

Chohaki is not full of it. He's built a few rotaries in his time and besides, there are plenty of peeps who have cracked irons without breaking an apex seal. I'm one of them...twice.

 

I wont argue what he has or hasn't done - I dont care about that.. but under the original context that irons are breaking (not the apex seal) due to pre-ignition or detonation - i dont agree with that. I can agree with rear irons breaking altogether separately of ignition related problems however.

so if this guy is not full of it, he can explain how pre-ignition or detonation will/can/could/might/kinda/sorta break the iron(s) without damaging the typical apex seal at all.

 

hwnd, I don't know why you're giving me all this crap? Not sure how I offended you?!

I was just trying to help the OP reach a decision, but you keep on resorting to insulting words when you disagree with my statements.

I don't have to prove anything to you, nor do I have to tell you what I've done, who I know, etc.

You don't have to search very hard for yourself to find the proof for what I was saying, but I'll throw something out there for you:

https://www.rx7club.com/showthread.p...ht=s475&page=7, look at post #155 and below.

It's ppl like you who turn valuable contributors away from this forum, you're entitled to disagree with someone, but there's no need to disrespectful. Anyways, I'm done with this thread.

 

This is in fact possible. I had built a motor for my car a while back and due to to tuner error (had 4 injectors turned off) i leaned out and split the rear iron. Pulled the motor apart and the rotors were trashed. I got another rear iron and a set of rotors and slapped it back together with the same apex seals. About a month later i had the car on the dyno and it made 764hp @ 30psi. I pulled the motor down to build it right and I still have the seals setting on my dining room table

 

8.5 S4 TII rotors have less of a chance detonating under boost. More boost can be run as well. We also need to rebalance the whole rotation assembly. S4 rotors also weigh more and will cause extra load on the crank.

Personally, the 9:1 stock rotors are fine for boost 19 PSI or less boost. 30PSI in a 20b will be putting down 800+ HP, I would go the 8.5:1 route in that case. 18-19+ PSI seems to be the limiting boost factor for me when engines blow up. I maybe get ~10,000-20,000 miles out of them. Running Methanol (M1) injection now in the IC piping, so we'll see how well 20-25 PSI runs do.

Corky Bell wrote a book that explains all of this better than I could.

 

that book is something that i've always wanted to read and i intend to do so before i close my eyes, but i still maintain that it's a matter of taking care to tune the engine. i'm not trying to dispute their merit or significance. however, their superiority at known power levels is surely questionable when you consider state of tune - that's all. this is just like the apex seal argument, it comes down to a matter of tuning style and overall preference and i'm not one to judge, but it's not conclusive that you can't make reliable power on the 9.0s.

there is no doubt that the lower compression rotors will match peak power of the 9.0s (albeit at higher boost), but they are not NECESSARY! you guesstimated 800 HP at hight boost on a 20B, well consider that a 13B comes very close to that (with 9.0s at high boost), too - and stock-ported, at that.