turbo, boost, EGT, water/meth ?'s
 

Hey all, im about half way done with my turbo build and things are staring to come together and look like a car again! but there has been something that ive been thinking hard about. What is the reason a rotary will crack rear plates or blow up with boost? My understanding (probably wrong) is that heat is the reason for blown engines with boost. A few members on here told me not to push a 12a past ~14ish psi with a T2 turbo. Is that because the EGT would get too high and blow it up, or is it actually the pressure inside the engine? If it is the heat, couldnt you use a water meth system to squeak a few more ponies out of it or not? Someone please enlighten me :)

specs on the build? Is it carb or EFI?

its more to do with week irons, comp. ratio, and tuning.

A stock s4 turbo is only good to about 10 lbs and an s5 a little more. iirc

many factors, listed in the order of simplicity....

the turbo. an FC turbo is small, its designed to run around 6-8psi, it'll do 10psi, but more boost and efficiency goes down, so basically air temps go UP which is bad, and airflow doesn't change much. there is a sweet spot with any turbo, and the FC turbo its in the 6-10psi range

cracking plates. USUALLY the cracked rear plate only happens with certain ECU brands. for example the power FC doesn't crack dowel pins. its a mysterious phenomena, but it seems to have something to do with ignition control, most likely the trailings triggering 180 off. the stock distributor is good, but its good practice to keep the plug wires away from each other, stuff like that.

blowing up with boost. EVERY engine, piston or rotary can do this one! when the factory put a turbo on the 12A they lowered the compression, you're not. they were worried about detonation @8.5:1 compression, you should too.

so what does this mean? this means that @10psi, you don't have to do anything too special, it needs to be rich on boost, and the stock NA timing might be too much, with a distributor it needs to be pulled back.

more than 14psi, you are getting in the area where you need to have things right, tuning, the right spark plugs, etc etc

i have bin run 12psi all summer with a s5 turbo welded the stock wastegate closed and running an 44mm external wastegate...in the springtime outside temps were like 70... afr of 11.6 at fullboost i am making like 270....now that it is much hotter outside i richend up the fuel running afr of 10.7 much slower....if you are running msd boxs you must run the wires in aposet direction of each other to the dizzy.....water injection is the key....when i get more funds i will be running pre turbo......my timing is (L)10....(T) 0.....sprak plugs are BUR9EQP all around...pm me if you need to get your dizzy locked the right way..:) and one more thing make a cold air intake.....:icon_tup:

Conventional wisdom says rear dowel plates just can't handle the power. j9fd3s has an interesting theory on it however. That said, most plates I've read about were in the neighborhood of 350-400hp, again conventional wisdom.

Boost issues, and water/meth injection target a totally different problem: detonation.

I've never messed with boosted 12A's but on my 87-88 13B turbo, which has weaker casting than later turbo 13B's, I never cracked an iron after multiple detonation events on stock ECU and Power FC. The old Haltechs (E6K for example) aren't too forgiving when it comes to the crank angle sensor signal.

my car is an 83 gs model stipped of everything unnecessary except it has full interior. Its not being built for any type of racing or anything, its a weekend/street car, not a DD. Ive never had a turbo car before, or a carb'd car, or a rotary (it was my first, ive since had 4:) ) so I figured id do my research and build something from the (almost) ground up. I swapped the rear end for a gsl (small bearing :/), made my own sump for my tank, 3/8 feed and return lines, summit high flow EFI fuel pump, mallory boost referenced regulator for my fuel system. Turbo prepped nikki carb (done by me), Im making my own carb hat, the turbo is an S5 and im keeping the internal gate but porting the hell out of it, 3" DP to 3" magnaflow. crushed and shimmed oil pressure regulators, 17mm oil pump, s4 oil cooler, locked Dizzy.. theres a lot more, but basically thats my build right now. Id LOVE to have 250RWHP on the stock 12a, am I dreaming? or does my goals seem realistic? I was just thinking when i asked my questions, what is the biggest limiting factor in power in a 12a? so i asked :) thanks for all the inputs!

so do you have water injection now? or are you planning on getting it? say your making 270hp, if you get water meth, could you push it farther?

also, a cold air intake I was planning on, what does the stock boot from the turbo inlet look like? also, what size is the stock s5 IC piping?

the 12A turbo's do about 240hp @10psi, so assuming you get the tuning close, it'll be really in the ballpark.

there are 2 limits in power with a stock 12A. rpm wise its the apex seals, the cast iron seals do not like to rev, if they aren't new i'd stick to 7200rpm.

the second is probably fuel/detonation. i didn't see an intercooler? start with stock boost, get THAT tune right and then work your way up

look like you have all your tee crossed ....no i don't have w/i yet. it on the list...i am not looking for more power..just want to cool down the engine with water..i don't have any pics of the stock intake to show you..this is what my c/a intake looks like....Attachment 438176

[QUOTE=cshaw07;10734427]so do you have water injection now? or are you planning on getting it? say your making 270hp, if you get water meth, could you push it farther?

not the engine i have in my car now....next on the list..Attachment 438177

for next summer..:)

oops! i do have an intercooler! Im unsure of the brand, but it doesnt look too pretty... i paid 40 for it used because the kid sold me a greddy S BOV for a steal. He said he bought a turbo talon that had the cooler on it and was making about the HP level i want but Im unsure if Im going to use this one or buy another.. im using 2.5" IC piping and plan to route it the exact way rx71king did his (rx71king - have you tried that with stock rad? did it keep it cool?) I dont plan on reving it much over the stock redline, as again this is just my fun car :) Im hoping that with my set up and a proper/conservative tune at about 10-12 psi i can be making 250rwhp reliably.

it all depends how good you tune that nikki.......i think 200 to 220 on stock ports

look..https://www.rx7club.com/showthread.p...bo...don't rev past 7500 rpm....and that's on the high side..read coldy13 threads good info for you....https://www.rx7club.com/search.php?s...08866.....good luck

Water/Meth kits help with detonation by increasing the octane level of the fuel. Also the water/meth cools the intake charge down. i run a snow performance water/meth kit on my 90 Eagle Talon. World of diff. I am planning on turboing my rx7. do a search for TT FB......:) Im also going EFI. Ill be doin a thread on that when its up and running. Just been running into problems:(

i saw your thread about the TT FB. hows that working out? How much did the water/meth lower your EGT's?

The stock turbo you're using is but about taxed at 10-12psi. I made 250whp on a 6 port 13b, with aggressive streetports, big intercooler, 3in exhaust, s4 turbo @10psi, on a haltech e6x.

Any more PSI than that on a stock turbo is just hot air, time to get a hybrid or big single. I don't think a stock 12A will get 250whp based on my experience. I think 220-230 is a good estimate.

But worry not, my miata with 200whp is quick, and my 7 with 250, was FAST.

What is your oil line set up? I saw what you're doing with the restriction on the turbo, but why the 17mm oil pump? Where are you getting your feed from and where are you routing your drain? Are you using the Nikki? If so are you boost prepping it how Bad83 posted up on how to boost prep it?

mine dyno 337 WHP at 10 PSI.

you have what all 12a boosted guys want......8.5:1 rotors....:nod:

Cool story bro. Not with a stock s4 turbo it didn't

I dont have a EGT probe on the talon so idk how much lower it got the EGT's all I know is that with it on she is a different machine lol. The Build is going slow of course. Im waiting to get her running on EFI before I finish up the turbo setup. I have two sets of twins with everything I need. I have a 3" DP. Wideband, FMIC and or Air/water IC. Walbro 255 inline. Just need to finish up the FI get that tuned do some tucking of wires. And finish moddying the exhoust housing to fit the 12A. So much to do lol. Shell be done some day and it will be amazing:)

:lol: T72 turbonetics BB

yep i got lucky i found a set of low compression 12a rotors