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View Full Version : Medium Size Turbo - No Fuel Mods



G-man
01-07-2005, 12:38 AM
I have a JDM gen 2 3sgte swapped into my 6th gen. My mods are front mount intercooler, FCD, MBC, MR2T tranny w/ LSD, 2.5" mandrel bent exhaust. That was stage 1.


I am now prepared to buy an upgraded turbo - specifically a T3/T4 46 trim .63 A/R with a 44 mm Tial external waste gate. I am also going to go EBC. That is stage 2.

This summer, I want to get bigger injectors, a fpr, fuel rail, and stand alone, and a good tune. That will be stage 3.

Q1. Can I do stage 2 safely without fuel mods? If so, what should I do to make sure its safe?

Q2. My goals for stage 3 will be 325 whp and 275 ft/lbs torque with a 200 ft lbs at 3500 rpm or below. Are there any other mods I should consider for safety/reliability?

Thanks for your replies.

skreem
01-07-2005, 04:43 AM
A1. as long as you dont crank the boost up too much without upgrading your fuel system i dont see the harm that could come to it.

A2. Maybe get a set of forged pistons

Spud
01-07-2005, 06:12 AM
agreed. It all depends on how much boost you wanna run. That ECU/fuel system is good up until about 275whp (to be safe). Not sure exactly how much boost that'd be on a t3/t4 and your current mods. 15lbs maybe? You'd have to find some dynos to be sure.

Once you have the stand alone and fuel upgrades you'll be all set for low 300whp for sure. Modest fuel upgrades would be fine even. (assuming you're all set at 325whp, and you have the stand alone)

Fox-N-It
01-07-2005, 08:47 AM
Fuel before Boost. Thats what i've always done. Better safe than sorry.

ChrisD
01-07-2005, 04:08 PM
A1. Just make sure to restrict the amount of boost you are running. Best bet is to run low boost until you get tuning and can ensure that you aren't leaning out on the stock fuel.

A2. Lots of things. It is far better to make the same amount of power with less boost. Two big things that would help would be cams and an aftermarket intake manifold. Big gains have been shown by both mods. Other things like water injection could help with keeping detonation under control as well. Instrumentation is always important. Load yourself up with high quality gauges. There are times that I wish I had had some. Now I do. Learned my lesson.


agreed. It all depends on how much boost you wanna run. That ECU/fuel system is good up until about 275whp (to be safe).

I wouldn't say that. Although the stock fuel system is capable of producing 275whp, that doesn't mean it is "safe" by any means. Remember this number is achieved at 100% duty cycle, a point at which injectors have trouble maintaining, can freeze open easily, and struggle to make consistent A/F ratios. Possible, just not safe.

:)

Spud
01-07-2005, 05:26 PM
what level would you suggest then chris?

I was going on what I've been reading on the MR2 boards.

G-man
01-07-2005, 05:32 PM
Two big things that would help would be cams and an aftermarket intake manifold.

If cams are installed, do you lose some of your drivability? I have heard that cams can make a car idle rough.

ChrisD
01-07-2005, 05:44 PM
Hehe well saying an actual number is harder. Best advice is "do you feel lucky?" :hehe:

Well you want to protect yourself from inconsistencies in the A/F. Best bet is to give yourself some breathing room so that if one injector does go lean, you won't blow the engine. I would say 250whp at the maximum (unless you are doing tuning with increased fuel pressure...but that wouldnt be on the stock fuel system). The thing is, the injectors are wide open at 275whp, but also at 235whp or even sooner. This is because the AFM reads the exact same amount of air at either power level. How come? It is because the AFM is already fully open at either point. That is why people always complain about how rich the 3SGTE runs from the factory. The AFM is wide open, so the injectors fire at ~100% duty cycle and theres nothing you can really do about it. You *could* tighten the AFM, however then you might go lean or have too much timing advance in places you don't want to (DISCLAIMER: I DO NOT ADVISE ADJUSTING THE AFM UNLESS YOU ARE A QUALIFIED ENGINE TUNER AND HAVE THE TOOLS TO PROPERLY TUNE FUEL AND TIMING). So anyways, at 235whp when you are pig rich, a little inconsistency would not be noticed at all and won't hurt your engine. It isn't until the fuel starts to lean out at 275whp that one small change in the amount of fuel could spell out catastrophe.

Regardless, ~100% duty cycle is generally regarded as extremely unsafe by most people and the injector industry. However, people with the 3SGTE do it all the time without really knowing. Maybe we have really good injectors? Consider that until recently, RickyB only sold his EMS systems with a maximum allowable duty cycle of 85%. He has changed it since then, but he has warned people not to exceed that limit.

Best to play it safe is all I'm really saying. If you are looking for more than 250whp, expect to do some fuel tuning in one form or another. It's still not risk free, but most get away with it without issue. :)

Good to see ya posting around here Ian!

ChrisD
01-07-2005, 05:47 PM
If cams are installed, do you lose some of your drivability? I have heard that cams can make a car idle rough.

Not if it is tuned properly. I have sat in an ST185 with Autronic EMS, 264 cams, and it idled like a baby. It was smooth as butter, just as smooth as my car. It's all in the tuning. :)

They do move the power band to the right slightly, but you also gain power with them.

Hooligan
01-07-2005, 05:58 PM
Common acceptable maximum injector duty cycles range from 80-85%.

A 264 cam is not THAT big in the grand scheme of things. Like Chris said, cars can still be made to run like stock with that size of a cam. 294s, however, are another story. There's a guy around where I live that has a swapped 6th gen with stroked 2nd gen 3SGTE that has 294s and a proper standalone tuned, and he needs to warm the car up before he drives it. After the engine is warm, it's pretty close to stock idle.

Spud
01-07-2005, 06:14 PM
thanks for the reply Chris. Didn't mean to give any mis-information. Most of the MR2 guys push their stock systems pretty far. I've been told (and do know its wrong, heh) by guys over there that 18psi with stock everything is "safe" to run etc. And lots of guys are running 275whp or more on stock ecu and fuel systems. I think you probably said it best by the phrase "do you feel luck?".......

Spud
01-09-2005, 05:47 AM
Chris,

Hopefully you see this. I'm sure you're aware of this site, in fact, pretty sure you told me about it a long time ago, haha. Anyway, he's very well regaurded in the 2 community, and sites 275rwhp dozens of times as being the ceiling for stock systems etc. (proper steps taken of course)

http://www.mrcontrols.com/primers/power.htm

Mind discussing it some more?

ChrisD
01-09-2005, 06:22 AM
Hey Ian,

Yep I'm well aware of Ricky's write up. It is very well written, although I don't exactly agree with everything he says in there. I wrote a fairly in depth critique of the power primer a couple weeks ago, posted here: http://www.celicatech.com/forums/showthread.php?t=1078

I've already closed that thread, but I'd definitely be willing to chat about any questions you (or anyone) might have about it! :)

Chris

Spud
01-09-2005, 06:50 AM
thanks buddy. Looks like I have some more reading to do :)

ChrisD
01-09-2005, 07:29 AM
No prob! :)