Question for the open source tuners out there.

[McDowell Performance Tunin]

I've been tuning my car via OS for several months and have tweaked my map to where I am not knocking while doing 3rd gear pulls or daily driving. I am wondering which approach to take to get a bit more power. I'm at a pretty high altitude (4,500ft or so) and wondering if anyone tuning their own car has experience with similar conditions. I'm running a pretty high WGDC 85% max, and about 17.5 PSI boost. I know the turbo (VF40) will be limited to a certain point because of the altitude, so is my timing going to be the best thing to adjust? I know I can get a smaller restrictor pill, but am trying to avoid adding anything else to the car. Right now, all I have is an STI UP and gutted 1st cat on my DP. Would gutting the last cat make much of a difference? I can run catless here without failing emissions, which I just discovered when I had to have an emissions test a few weeks ago. (they only check the OBD-II for CEL's). Anyway, I'm starting to ramble so I'll wrap this up. Here is my dyno graph, using airboy's spreadsheet and 60-80MPH time. Also, my last LV and 3rd gear pull. I'd appreciate any feedback from you more experienced OS tuners and as always, thanks for any help, or constructive criticism .

romraiderlog_20100308_215308.csv

[Boostin1657615274]

why don't you just leave well enough alone? You can crank up the boost a little more but that's going to reduce the life of your turbo. You can add a bit of timing here and there but don't expect big gains. And knock isn't good for engine life. Now removing the rear cat should result in some gains and isn't going to hurt anything as long as you keep an eye on your boost control tuning.

 

The key to having a reliable setup (and this applies to any performance car) over a long period of time is to NOT do what you are asking to do: squeeze every little bit of performance you can out of your components. Most people don't understand this. The turbos and intercoolers already have reliability problems. Just be happy with what you have.

[McDowell Performance Tunin]

Right, I'm not pushing the car very hard as it is. 17.5 PSI of boost is relatively low for stage 2. I'm really not interested in raising my boost any higher or "squeezing every little bit of performance" to the brink of engine failure. If you Look at my LV and log, you can see how safe my tune is. The knock count of 8 was just starting the car and low speed driving, i.e. not actual knock, which you can see from my feedback knock correction. My AFR #'s are about as good as you can get and I'm pulling absolutly no timing. Deleting the third cat is probably what I'll end up doing, but you should know that what I have done, or am doing to my car is NOT going to shorten the life. I log everyday and know exactly how my car is running. I'm not trying to sound like an ass, but your last paragraph is not really anything someone who is OS tuning their car already knows. There's always a risk when tuning, but that's why I use logging and LV daily. Basically I don't need a lecture on doing stupid things to my car. Sorry if that's not the way you meant to come off, but I'm not an idiot. My car is probably safer now than stock, now that my catted up pipe is gone and my daily monitoring to make sure everything is running the way it's suppose to. I've also recently checked my turbo play, intercooler tabs, vacuum lines, belts...you get the picture.

[John M]

That may be true if the VF40 wasn't such a POS to begin with. An extra psi very well could halve its useful lifespan. You don't usually get the luxury of a warning before it lets go either.

 

I vote for leaving well enough alone.

[McDowell Performance Tunin]

Right, like I said, I'm not planning on adding any more boost...thoughts on going completely catless, John?

[Infamous1]

Right, I'm not pushing the car very hard as it is. 17.5 PSI of boost is relatively low for stage 2.

At 4500ft it is actually pretty aggressive. From a compressor map stand point it wold put it in the 18.5-19 psi range at sea level.

I agree with everything Boostin stated. That being said you are nowhere near your stated boost in the log posted.

[Boostin1657615274]

On the knock issue, yeah you can definitely avoid that if you're careful and know what you're doing--and I saw your learning view, I know you're not detonating right now. Which is exactly why I suggested you just leave the thing alone.

 

But there's no way you're not going to shorten the life of your turbo and intercooler with more boost. It's designed to run around 13psi from the factory (peak). You've cranked it up to 17--that's certainly not helping its life, but it's not particularly high for a stage 2 setup. The high altitude does make it effectively a higher boost level than 17. But you're reaching a point of diminishing returns, where increasing the boost stresses everything more and more while returning less peformance benefits. Any component on any car is like that. There is a safety margin built in, and the more you cut into it the more you reduce the component's life. IMO in your situation you've already done a good job with the tune.

 

Eliminate the rear cat, check the tune, and call it a day. You've got to know when to say when. That comes from years of experience tuning sequential twin turbo and single turbo Rx-7's.

[John M]

I can't speak to gains from going catless as I willingly chose a catted downpipe. My reasoning was that it would make very little impact on power while keeping my emissions somewhat clean, even though we don't have testing here.

 

I don't know how much of a restriction a stock cat poses while still on the stock turbo.

[McDowell Performance Tunin]

Ok, sounds good. Like I said, I'm not intending to raise boost. Also, I too have noticed I'm not hitting my boost numbers. (that's why I have it set a bit high). I've checked and re-checked for exhaust leaks, but cannot find a trace of it anywhere. I've also done a vacuum test throughout the intake system, but everything is fine. So, if my manifold relative pressure is consitantly in the 15 PSI range, should I lower values for my boost? I don't mind doing that, if I'm beyond what the turbo can handle. I guess that's what I was getting at when I originally posted this page. Everything seems great right now and if I could safely get a bit more power (I figured gutting the 3rd cat would be the best method) then great. If not, that's ok too. I like knowing I'm not knocking and that my AFR's are where they should be. Thanks for the tips everyone. I'm still new at this, but I've done all of the work to the car myself (plugs, up pipe, and the pain in the ass kartboy shifter bushings) so it feels good to know with a bit of elbow grease, a used $60 STI up pipe and a $15 dollar cable, I've managed to get my car to a safe tune and much improved performance. I'm so glad I didn't buy the $700 accessport. You guy's t=have taught me a lot and I couldn't have done the work without all of the writeups and advice. Thanks guys.

[McDowell Performance Tunin]

I've been working on bikes for years, both dirt and street, but a turbo charged car is much more complex. I'll eventually eventually end up doing a bit more (full turboback, upgraded turbo, intercooler, fuel pump, injectors, coilovers, brakes...I'll stop there for now) but I plan on having this current set up for a few years.

[SubyShop.com]

Right, like I said, I'm not planning on adding any more boost...thoughts on going completely catless, John?

 

Proper oil change interval and maintenance goes a long way. I have been running 20 PSI on my VF40 for over a year now (was OTS stage 2 before that) with 56k miles and still going strong. Of course, I probably just jinxed myself.

 

When I went catless, the butt dyno said 10-15 HP but the downpipe size also increased by .5" to 3"

-Franz

[McDowell Performance Tunin]

Yeah, I'm very anal about oil changes and maintenance on my car. I have done everything on time, or early. I always keep all of my recipts and documents. In fact, just changed the oil last week.

[McDowell Performance Tunin]

I also check weekly the oil level, to make sure I'm not running low.

[McDowell Performance Tunin]

Also, how do my HP TQ numbers look, as far as my mods, are they about where they should be? How about the 60-80 time?

I posted those to go along with my first post to see if the numbers look low, or about right.

I've seen the 60-80 50-80 post, but everyone's numbers on there are extremly fast compared to mine, granted they also have a lot of mods.

[keithk831]

You're only hitting 14.95psi on a custom tune? I have the same setup and i'm hitting about 15.8psi on a Cobb Stg2 map. I'm using Manifold Relative Pressure (Corrected), though. If that makes a difference.

 

http://www.legacygt.com/forums/showthread.php?t=133010