87-89-91 or 94 octane?? as im sure its been covered and recovered many times. im just looking for ppls input on this one. im doing a megasquirt in July or august and tuning from the ground up using the stock turbo at around 8-10 psi with a big 3" front mounter 88 Volvo intercooler so my intake air temps should be lower then stock S5 top mounted intercooler.
since there is 8.5 cents per Canadian letter in difference between 87 and 89 octane id like to tune with 87 octane but would i risk detonating the engine with the lower octane? or would i be fine.
I know im driving a sports car and tuning/ moding the car so i should expect that its not going to be a gas saver but just trying to save some $$ like the rest of us

thanks for your help.

 

Remember, the TII runs 5.5 PSI from the factory and Mazda says 87 is fine. However once you start increasing intake temps (like the stock turbo does dramatically when you raise the boost) having a more detonation resistant fuel is very important. Intake temps will ultimately decide because if your temps are close to ambient with the big intercooler, you can probably get away with 87 octane on conservative timing and a rich tune (basically what Mazda does). However, put 91 in it and the tune doesn't have to firehose fuel into the car to keep the engine together. The difference between running 10.5:1 in boost and 11.5:1 is dramatic.

I run 91 in my car.

 

Yeah, we've been running ~11.5:1 @11-12 psi on eage8's (Myk's) car, but we started out about where the factory runs it... the difference was about 20 HP on a dynapak dyno. Going any leaner didn't help at all either, so we kept it right around 11.5. Myk runs 93 octane (premium on the east coast is usually 92-93 octane, and happens to be 93 where we live).

Ken

 

I run 93, just for that extra safety factor, and since that little bit of extra insurance really doesnt cost much. Right now im at the stock 6 psi, but i will be running 12 soon.

 

Once Myk gets his front-mount intercooler installed, and we get the MS controlling boost, we're going to tune for 15 psi. I may add some code as well for making boost tables switchable using a toggle switch for a high-boost and a low-boost setup. Or Myk could just keep his foot out of it and help his fuel economy.

On the dyno at 11psi, on a power pull to 8000 rpm, Myk's MAT would go to 160F, and the air-temperature-based timing retard feature would pull a little bit of timing.

Even still he was able to hit about 270 RWHP on a dynapak (often called a heartbreaker).

Ken

 

160F?! That must be a stock turbo...

I was tuning a friend's 1st gen with a decent sized front mount and a China T4B running MS1 last weekend and our intake temps were basically ambient (90 degrees). Only 10 PSI though. I think a new wastegate spring goes in tomorrow night so it should be 15 PSI this weekend.

 

It's a BNR stage 2

The stock TMIC is useless...

 

Wounder what the differance will be in air temp and coolant temp with the FMIC installed? On the dyno iam sure u will see a differance driving (real world) i wounder!I was setting up a front mount on my N/a getting ready to install my t2 engine and freeking water temp jumped by 25 deg's 215 220 range w/o a/c on,same day with no FMIC it ran no hotter than 185! I must have got it hotter at some point cause i blew a coolant seal and broke the front and center irons on the front rotor (coolant seal ring area) fyi that with stock cooling set up ,fan, shroud, rad extra!Dam FMIC blocked to much of the air flow to the radiator but then again it was like 4 inches thick!

What are u see air temp wise running down the road with the TMIC?
Mine get up to 153 at idle but at 11lbs its at 116 when it 85-90 degs out!

 

Coolant temps?

 

no, intake air temps.

 

I'm running 98RON (research octane) which is a different rating system to what you guys use, its our highest grade premium here in Australia.

I have 12A NA block, turbo port, 9.4:1 rotors, and a stock S5 turbo flow maxed. I'm running on the rich misfire limit with the best petrol I can use. My boost peaks out at 13psi 4000rpm, stays flat until about 5250rpm, but the turbo is way undersized and boost drops to 7psi by 7500rpm. Peak power is very wide and not much can touch me on the street. I have raced and beaten 13BTs with highflows at the track too.

I have a big cooler and a POD under my front bar, my inlet temps are close enough to ambient. Def under 80degF on a cold night. I don't think theres another 10HP to be had without a bigger turbo.

I got the car weighed the other day as I race it. 1160kgs loaded with me thats 2575lb! (105kg atm :P) and a full tank of fuel. I've already trapped 109MPH @ the 1/4 and a best time of 13.362 (on a different and messy run)

 

well looks like il just use better fuel thanks for your inputs

 

http://www.youtube.com/watch?v=P12jwypWL5U

I was trying to get a 12.99 :P

Left is twisted and snapped, right is twisted.

 

:O thats my next weekest link i just got a good drive shaft fabed now im scared as im at the hp now i think acording to my 14.2 1/4mile time that scares me some