Modifcation Q's

Well, I have a 2004 WRX wagon, i am in the process of picking out a muffler to have nathan build me a turbo back setup, I have already bought an up pipe to go along with the install.

My question is if i would get larger injectors or get mine modified but stay running the stock turbo, would i see any real noticeable gains. Understandingly i know i would have to get a tune done for my car.

The key is that this is first of all a daily driver, secondly I am going to start auto x this year:biggthumpup: and would like to class in ESP, (at least that looks like were i am going to be maybe zack, stooo, or some of the other mac guys could help clarify if this is right).

I am in the realm of thinking that i would like to have the turbo spool faster and have less hp but quicker response time for running an auto x.

Is anything i said above correct or is there any advice you guys could give, it would be really helpful.

 

With just a turboback you wouldn't have any noticable gains by upgrading the injectors. If you were going with a different turbo you would definately need to upgrade the injectors.

If you are AutoXing a WRX, get an STX legal tune (no boost changes) so you can run street tires and be competitive. If you need to up the boost you will be in ESP or SM depending on what other mods you have done. More than likely ESP will be where you end up.

 

I know i cant run in STX because i dont have any cats. Therefore it isnt emissions compliant. I may be wrong, but that is how i read the classing rules.

 

ST classes do require cats, so you're right there.

The MAC forum has a special area for Car Classing and Rules questions. If you ask over there, you should get an answer fairly quickly. Just keep in mind that you'll most likely get a bunch of other advice you weren't expecting.

For those that may not know, MAC runs a special class for cars on street tyres that would be classed in non-ST classes normally. For example, instead of being in SM and buying R compounds, you can run in SMt with a set of Azenis. Likewise an ESP car could run in ESPt. All of the 't' cars compete as one group, with PAX index numbers applied according to the cars normal classing to even the field up.

Alternatively, if you're just in it for the fun, you could do whatever you want to the car and run in SI. But only until you win.

Stuart.

 

What is the cheapest yet reliable way to get a set of injectors, I am trying to do this on a pretty tight budget.

 

Modded stockers.

And yes, there is quite a bit more power to be had once you increase your fueling capacity.

 

will the stock fuel pump be enough or should i upgrade to the walbaro pump if i change the injectors?

 

ditto on the pump

 

mglez did injectors and fuel pump when he did stage 2, and IIRC the pump helped out a decent amount. i would say do teh pump too they are pretty easy and relatively cheap.

 

Who does the injector mod, was it WRX1 (Russ), or somebody else?

 

yep, he's the guy.

 

Changing your injectors will bump you into SM for AutoX.

For those that have tuned more than I have- how much power can be gained by going to larger injectors without swapping the turbo? I am thinking that 10hp isn't really noticable. Maybe I just need my butt dyno re-calibrated.

 

Here is what i got from the scca solo handbook. From my reading it looks as if i can change out the fuel system.

Street Prepared – The original SCCA “street†category, Street Prepared allows
any carburetor or fuel injection system and any ignition system. Turbo /
superchargers have to remain factory spec as well as boost control systems,
except aftermarket intercoolers are allowed. Exhaust manifolds and systems are
free. Emission controls are not required for competition, but no internal engine or
transmission modifications are allowed beyond factory specs. Some cars are
able to update/backdate components like engines, brakes, etc. (See Solo Rules
for details and specs). There are no limits on wheels sizes or DOT tires and racebred
springs and shocks are the norm.

 

I wonder if the fuel pump counts as part of the injection system. You could run that car in ESP with the injectors. I'll be the only other real competitor there, but if we can pick up one more car it would be a whole class (classes bump up unless there are three cars competing in it)

You're probably going to want to compete in SI, the novice open class until you gain enough skills to win that. usually the top SI times are lower than the average times that car would run if it was normally classed.

also FWIW there are STX tuned WRX's that are pushing 245WHP. that's on stock boost, so its doable to have it fast. And if you have an accessport you can flash to your STX map when you get there and then flash off of it when you leave, so you dont have to constantly drive your car at stock boost levels.

 

I'm working on tuning my car with Russ-modded stock injectors (705cc/min) and the stock turbo. I'm still working on getting my fueling dialed in right, I can let you know what happens when I start tuning up the boost. Modded injectors don't quite flow linearly, especially on the low-flow end (i.e. idle) so you have to futz with your MAF scaling or fuel targets to get it to run right at both idle and wide open. Once I get the gas map reasonably well tuned, I'll be switching to E85 which should give me quite a bit more power than gas at those boost levels.

 

I looked at the same rule and completely missed that. Looks like ESP is the class for you. Much better PAX than SM.