iceblue

I think I know what you are talking about. I do not know your answer, sorry. My guess on it is that it is irrelevant.

JoshRX7

iTrader: (5)

I don't think it's irrelevant... here's a 12a guy (9.4:1) that seems to know what he's talking about... he mentions he contacted Racing Beat as an authority. I know some of these components that he mentions are already present on the 13B, but you can't deny the effect of heat of compression at the rotor dish.

Follow this thread: https://www.rx7club.com/showthread.p...igh+output+12a

The short of it:

"Okay, this is the third time I have taken my engine out and torn it down, and it is starting to get old. Most recently, I was puting out 300+ horsepower at the engine and suffered from loss of compression. When I took the engine out of the car, and tore it down, I found the reason that my compression was low was the corner seal springs were FLAT. The corner seals were essentially not functioning. I wonder how the hell the engine even produced 55 psi of compression! So, I called Racing Beat, and found that they were flattened due to overheating of the rotor. So, now that I am rebuilding my engine for the third time, I have finally found all the things you need to build a 12a with more than 200 horsepower, using forced induction.

The most essential thing needed to keep your engine reliable under these high thermal loads is COOLING!!! I can not stress this enough! The reason my springs flattened was because of the high heat caused by compressing air in the engine, and further compressed by the rather high 9.4:1 rotors (not exactly thermally efficient for a forced induction engine). This causes the seals to anneal, softening them, and basically weakening them. To counteract this, you need to keep the inside of the engine cool."

rx7idgit

Ignore me.

JoshRX7

iTrader: (5)

Well, you need to look about 7 posts up where I apologized to Iceblue for any rude comments I made. I ain't made at ya. And what is not useful about this thread? Maybe somebody knows all of this, but some of us are still learning something new about these engines everyday. I think we've made a good deal of progress in this thread today. At least I have in my own mind... I don't know what to tell you other than turn the page... and maybe read all the posts before posting next time.

Josh


Edit: Okay, you changed your post... ignored.

rx7idgit

I apologize, didn't see there was a second page and thought I edited before it was read, and I never said the page wasn't usefull.

JoshRX7

iTrader: (5)

Okay, cool. Contribute if you'd like...

Josh

BlueTII

First off the statement is "This allows for higher boost levels/more power then the N/A rotors" , which translated means that the use of TII rotors will allow the owner to push higher boost levels much safer then N/A rotors, higher boost levels equal more power.

In most cases, as is this one, the original poster doesn't really know what he is asking, which is evident from the "slap a turbo on" statement. There is much more to turbocharging an N/A then just adding a turbo. Once they find out that the fuel system, exhaust, intake, engine management all need to be upgraded, then the addition of an intercooler, this usually opens their eyes to the expense involved.

Most people that turbo their N/A engines, do so without rebuilding, so they are stuck with the high compression rotors. In this individuals case he has the luxury of having turbo rotors installed during the rebuild process, which in turn assures higher reliability of the engine. This also allows the owner to do the upgrades that a normal TII owner would do. The fact is that 250hp gets old quick, and people get the itch for 300 pretty easily once they have a taste of boost.

We have built several 9.4:1 and 9.7:1 streetported N/A engines that were setup for a turbo to be installed at customers' request. While we have the engine disassembled we drill and tap the front iron for the oil feed line, install a TII oil pump and assemble the engine with a TII front cover. Most of these engines have been built to run as an N/A with the option of turbocharging at a later date.

The use of the high compression rotors makes it inevitable that an EMS is required. We also strongly recommend a water/methenol injection system to reduce the chance of detonation caused by overheated rotor faces. It is much easier to have preignition at much lower boost levels with the high compression rotors. Even though the apex seals can hold up to the heat, the rotor faces can and do cave in (see bottom of page http://mazdatrix.com/faq/boost.htm)

There are always going to be people that will just slap a turbo on their N/A , they will cut as many corners as possible and end up with a blown engine. It may run great for a period of time, but if you do it correctly the first time it will run great for a long time.

BTW- the intake charge temp has nothing to do with which rotors are used, that is determined by the efficiency of the turbo and intercooler setup. 250F(121C) and 300F (148C) intake air temps will certainly damage an engine. For comparison my intake temps on the FD are never over 40C(104F) , with the water injection on they do not exceed 17C (63F)

iceblue

I agree. And I agree more boost = more HP and the same equation is effective for the NA rotors. You just will not have to push as much boost to make the same amount of power.

I feel that was to be latter addressed in another thread, or his responsibility to search the forum of the many turbo NAs to come to his own conclusion.

That’s how I build mine.

I have never heard or seen of this happening from heat on the face. I have only seen including MX page the face collapsing from to much boost or the housings stretching an smacking the rotor against it. This is all a case of to much boost on any engine.

Lets make them roll models of what not to do.

I am not to sure what you are saying here or who you are saying it too. I was never determining rotors with my temp statement. I was trying to explain to Josh about the heat involved and this was all pre intercooler jesters. Jrat sees intake temps of 40F with alcohol injection so there is a large margin. I was trying to show how the higher comps wouldn’t effect heat as drastically as he may have thought.

IMO this is to veg. The rotor gets like 98% of its cooling from the oil system. Did this guy upgrade his oil cooling system? His oil pump? Rotor bearing? Maybe he was running to lean without an injection form the rotor face is cooled by the fuel. What was his EGT's? What springs did he run?

I think this is an exceptionally informative thread for you.

JoshRX7

iTrader: (5)

There is a list of mods on the thread I posted about the 12A (9.4:1) guy. You should follow the link to see the mods... there are also naysayers on that thread which leads me to think this will never be a cut and dry issue. Although I'd think after you blow one, you'd probably do the mods next time.

Fitness Stain

pissing contest what?

iceblue

Here is the thread I started in contrabute of high comp.
https://www.rx7club.com/time-slips-dyno-128/i-want-see-dyno-slips-na-turbos-tii-high-comp-508696/

Silverbullet

well... after LOTS of reading and research (more than i've ever done in my life), and comparing similar cars and my budget, i've decided to go with another 240sx. thanks for all the help even though this kind of just turned into a big *** debate haha. but seriously i really appreciate everyone who was trying to enlighten me.

i think the rotary world is too bright and scary for someone like me. kinda sucks cuz 240 people arent really so helpful... but at least i know about them.

iceblue

Well if you change your minde the rotary community will always be here for you. Don't stray to far.