johnny O

Are there any other disadvantages other than the predetonation tendancies from higher compression ratio if I build 13b t2 using lighter n/a rotors? Tried to use search in FAQ and Tech archive to no avail.Please set me on the right path of wisdom

Aaron Cake

iTrader: (1)

The only lighter NA rotors are the S5 NA rotors, which are 9.7:1. That is quite a lot of compression compared to the 8.5:1 compression of the TII rotors. While I have a lot of experience with running 9.4 rotors in turbo form reliably, I have not personally done a 9.7 engine. I don't think I would want to, since others don't seem to be able to keep 9.7 turbo engines together for very long.

You're not going to get enough of an advantage with lighter rotors anyway. The slightly high RPM operation won't help much since you can size your turbo to produce a powerband within the operation range of the heavier TII rotors.

lastphaseofthis

iTrader: (8)

Also, if you do choose to use 9.7, or even the 9.4's, the stock ecu's timing will surely pop the motor, you will NEEED a standalone.

Evil Aviator

Just to clarify Aaron Cake's post, light rotors really only have an advantage on high-rpm racing engines, and many other high-rpm modifications are required in addition to the rotors. It is not worth your trouble to worry about high-rpm modifications on a turbocharged street engine, and high-rpm racing engines are not something that a noob should attempt to build without the direct help of an experienced mechanic.

Also, preignition and detonation are proper terms for engines, but "predetonation" is a misnomer unless you are talking about bombs.

RTRx7

iTrader: (2)

It's pointless. You could do it if you want, but you could make the same power with the turbo rotors. Your power will come from the turbo and your tune.

farberio

iTrader: (7)

Without knowing what you are running now, S5 TII rotors are just as light as S5 N/A Rotors.

Bwek

iTrader: (4)

I have my S5 n/a motor Turbo'd using all the stock T2 stuff I can honestly say I love it I have driven a T2 with similar mods and my car was wayy faster

just make sure you have a really good tune but dont be really expecting to throw a big turbo on it and make the same power as a low comp motor without blowing it up

then again theres always C16.. lol

johnny O

Thanks to all of you for your input. The engine will be for '87t2- that's an s4 isn't it? What little I know of the rotary engine has come from reading this site. If I understand your responses correctly, there is no advantage to be gained by using a lighter rotor in a steetable t2 rebuild, only the potential for disaster early in my learning curve. Evil Aviator, thanks for setting me straight on preignition. However I do have a history of blowing stuff up before its time. Aaron Cake, thanks for providing me with the correct method of maximizing the power and reliability from the heavier rotors in a t2.pr0x3tnta confirms this. I will be using a MS2-3.0 I purchased and built for a previous project per lastphaseofthis' recommendation. And Bwek, I'm familiar with C4, but what's C16?

Evil Aviator

Yes

As long as everything is properly balanced it will not hurt anything but your wallet, but it will not help anything either. Here is the progression: Porting the engine moves the power band up in the rpm ranges, therefore the redline needs to be increased, and in order to keep the engine from shaking itself to death high-rpm modifications such as (but not limited to) light rotors are required. Therefore, light rotors are not a performance increaser so much as they are the solution for the side effects of the power-increasing modifications. Stock porting or mild street porting does not require high-rpm modifications.

Also, have you driven turbocharged engines before? If you have, then you may have noticed that if you are at cruise and stomp on the gas pedal, the boost increases but the engine rpm doesn't go up all that much. This is because the turbo picks up the load and increases torque when the gas pedal is pressed, so engine rpm isn't as much of a factor as it is on non-turbo engines.

Excellent, finally another forum member with a sense of humor, wit, and self-confidence. Unfortunately, that means you are screwed for life, but at least you will find your own folly amusing.

It is similar to C4, but with uric acid in place of the RDX. It was used in the Khobar Towers bombing, and when formed into 5-micron ***** it makes a great fuel additive for rotary engines modified with a special titanium anti-detonation casing.

Hehehe, no, just kidding, it is a racing fuel product from VP Racing Fuel:
http://www.vpracingfuels.com/road-racing-drifting.html

johnny O

Hello Ev.Av. And Happy New Year. Thanks for your clarifications. I do already walk with a limp due to verbal torsions applied to my left leg for extended periods of time(Somewhat similar to the B.O.torsion you so aptly quoted). I have another question concerning the rotary and turbocharging I'm not sure of. Corky B's Maximum Boost states that the true advantage of turbocharging doesn't come from raising maximum cyl pressure during combustion, but from increasing the mixture density, thereby raising the combustion pressure "three or four-fold at crank angles near 90', such that torque input at that position can be twice as great". I grasp how this applies to the traditional piston engine's 720' rotation. It means that from apx 30' ATDC to apx 120'ATDC of the 720' there is an increase in torque to the crank due to "boost". Due to the three faces of a rotor supporting a different portion of the complete process simultaneously on two different rotors, does the rotary enjoy a longer duration of "boost" per 720' rotation? Or is the rotational "boost" duration more comparable to a six cyl? "O"

Aaron Cake

iTrader: (1)

I think there is some serious overthinking happening here.

If you have a history of blowing stuff up, then simply stick with the stock rotors. They will in no way be a limiting factor in making power. What are your power goals, anyway?

Going to the 9.4:1 rotors dramatically improves off boost driveability and turbo response but will be a lot easier to blow up if you don't have tuning experience.

Evil Aviator

See Fig 1.32
http://foxed.ca/rx7manual/manuals/RE...amoto-1981.pdf

I think the more important lessons from that portion of the book are that turbos create torque as opposed to horsepower, and that turbos multiply pressure as opposed to adding it. For some reason the general public has trouble grasping these concepts, most likely due to misleading advertising.

Also, some corrections and notes for "Maximum Boost":

Page 26
Pressure Ratio
Change 14.7psi (all occurrences) to actual barometric pressure.
Note 1: 14.7psi is correct only for standard sea level pressure.
Note 2: Standard lapse rate is about -0.5psi per 1000ft altitude.

Page 26
Convert PSI to Bar
Change 14.7 to 14.5

Page 27
Airflow Rate Equation
For rotary engines and 2-stroke engines, delete 0.5

I actually like his "Supercharged!" book a little better because it uses modern lbs/min maps as opposed to the old cfm maps. Also, I am quite disappointed that he pretty much ignored rotary engines in his books. Most people do not realize that he developed turbocharger kits for rotary engines back in the day.

johnny O

Greetings Aaron Cake. Please don't let me mislead you about my destructive nature, I've managed to keep it in check since the late seventies now, and beware of my SASH-smartasssouthernhumor- still out of control. And my question is still valid, does the unique trichoid rotor present a greater percent of 720' rotation to the combustion process most affected by the benefits of turbocharging? "O"

johnny O

Wow! Printing out Yamamoto's book right now. Where have you been keeping this? Exactly what I need to "get a grip" on the rotary. Thanks Evil Aviator- Can I call you EvAv for short? And I do think too much, so I owe Aaron Cake an apology twice,1-for not answering his questions first: - Power goals- for sensible streetable usage 325-350bhp that can be driven for reliable daily fun. 2- for badgering him when the info was on a link right in front of my face if I had only looked. "O"

Aaron Cake

iTrader: (1)

It's no problem. I have a twisted sense of humor as well but don't often show it in forum posts. For a simple 325 HP, then look at the BNR hybrid turbos. If your engine is already apart, give it a street port and keep the existing rotors. Then with a hybrid turbo and some fuel mods (RTek ECU replacement and injectors) you are looking at around 325HP. Around the 350HP level is where you start looking at full turbo upgrades (T4B or GT35R are good for those levels, I would go for the GT35R above all else) and a standalone EMS.

johnny O

And another Wow! Just hit Aaron Cake's personal page to thank him again. You folks will not believe what all can be shot out of a spud gun..... yes he's as twisted as the rest of us!