3rd Annual Subaru Shootout: Recap: MAF discussion

BAC5.2 · Post by **BAC5.2** » Mon Sep 20, 2004 11:22 pm

Vikash - Would a GM 3" work or no?

vrg3 · Post by **vrg3** » Mon Sep 20, 2004 11:29 pm

In principle any airflow sensor could be made to work.

In practice, we'd want to stick to hot-wire or hot-film sensors.

I believe the GM one is a hot-wire, so it should be fairly straightforward to make it work electronically. Physically it might be more of a challenge to make it fit.

BAC5.2 · Post by **BAC5.2** » Mon Sep 20, 2004 11:38 pm

I'll see if I can get it off of my buddy this weekend, take some pics, and get them to you ASAP. I'm sure that if you can figure out the electronics, I can figure out the placement.

vrg3 · Post by **vrg3** » Mon Sep 20, 2004 11:41 pm

Well, I'm not ready to start playing with them just yet... Maybe in a couple weeks when I'm in DC we can play a little.

Maybe you should change the title of this thread to include "MAF sensor discussion" in it or something...

BAC5.2 · Post by **BAC5.2** » Mon Sep 20, 2004 11:56 pm

Ok, in a couple weeks I should have the money to play around with it as well. I would like to do the fuel pump before we start working on the MAF, and hopefully I'll be able to pick one up by my birthday.

When, again, is Columbus day?

I'll still pick up the MAF from my buddy. It was mine to begin with, and I'm closer to using it on the Legacy than he is on his DSM.

The idea you brought up about the fuel cut thing being pump related is a good one. At 13psi, I wasn't cutting until the top of 3rd, and I can do a 3rd gear to redline pull on the highway without cutting anytime now. I think it's just that in the 1/4 I was taxing the fuel sytstem to much at 16psi, and it was cutting often (not necessarily 3 seconds apart. I didn't cut in 1st, or 2nd for some runs.) We'll see what a bigger pump will do, then just have to meter it out with a better MAF and some control for the injectors, and that'll be good enough for a little while.

corsair · Post by **corsair** » Tue Sep 21, 2004 12:01 am

d'oh guys sorry I kinda was asleap at the keyboard!
everyone has pretty much said how cool it was and how much of a fun time it was so I'd just be redundant... anyway I have the videos and stuff, we're lucky that it wasn't scheduled for sunday, the flooding got a little worse, including having parts of 15 north closed before and after lewisburg

anyway I'll IM Phil sometime and get him those videos and pics, they're worth it

thanks again for a good times guys

BAC5.2 · Post by **BAC5.2** » Tue Sep 21, 2004 12:05 am

Dang, there was some serious flooding on the way there! Town's were like underwater! Thank's for the use of your tail pipe Sam! Next shootout/F&S or whatever, when I have my car running well, I'll take you for a run down the strip.

georryan · Post by **georryan** » Tue Sep 21, 2004 1:39 am

azn2nr wrote:phill your pass was only 15 seconds but your trap speed are high 13. just solve your fuel issues and youll be flyin

I'm not looking at the trap speeds of a thirteen second car right now, so I could be wrong, but I'm doubting his traps are in the 13 second range. I trapped at 89 and 90 mph and I was only getting a 16.6 in the quarter with a 2.?? second 60' and a .3 R/T.

Those were my averages from one of my drags. My car wasn't full boosting the whole time in those races, but I always seemed to get around the same trap speed.

I think that if you were doing 13 second times you'd be closer to 100 mph. Just my 2 cents, but I'm not trying to start a debate. I'm just offering a rebuttle

vrg3 · Post by **vrg3** » Tue Sep 21, 2004 1:57 am

Phil - Yes, you should do the fuel pump as soon as you possibly can.

Columbus Day is something like the first Monday of October.

corsair - Yeah, Matt's mother-in-law was worried about me and Phil being able to get back home when we left Williamsport Saturday night. We made it though, apparently.

Oh yeah, I forgot to mention -- corsair came with me on a run (Or was it two? I forget). It's fun to race with someone riding shotgun.

corsair · Post by **corsair** » Tue Sep 21, 2004 1:59 am

just one run, despite the slow times on paper the seat-of-the-pants dyno said your car was fast

vrg3 · Post by **vrg3** » Tue Sep 21, 2004 2:07 am

Hehe... I think that run was the first one where the clutch slipped like crazy at launch and after shifts. Each time, once it started to grip acceleration was good.

BAC5.2 · Post by **BAC5.2** » Tue Sep 21, 2004 3:42 am

Ryan - I think he's saying that at close to 91mph, with such a bad 60' time (2.401 was my best), with a good launch, I'll be closer to 100mph.

Look at it power wise. I ran a 15.6, and trapped at the same speed as you did. A better launch, and I'd be cookin.

georryan · Post by **georryan** » Tue Sep 21, 2004 3:55 am

True. Very true.

When I had my stock exhaust and ran, i must have been capped at the wastegate by the ecu, cause I was getting times identical to what vrg3 got when he turned his down to 5 psi.

Also, by doing nothing but putting on the exhaust I picked up a second. Some may say that maybe my boost was acting better. Maybe it was, but I didn't have a boost gauge i don't think, so it could have been any number of things and I wouldn' t know it.

-Ryan

BAC5.2 · Post by **BAC5.2** » Tue Sep 21, 2004 4:02 am

I was pushing 10psi all the way down the track. My eyes were glued to the tach and the boost gauge (really cool having both on the same side of the dash, I didn't have to divert attention at all).

legacy92ej22t · Post by **legacy92ej22t** » Tue Sep 21, 2004 3:30 pm

evolutionmovement wrote:Yeah, I found bits of my valve stuck to the screen in the pan (lots of bits - you guys saw how much melted away) and a few in the cylinder, but none of those pieces damaged the cylinder wall. Even the valve seat is fine. If I put a new exhaust valve in, it would've done the trick with no other work but a thorough cleaning. So anyway, I'd think positive that the damage is isolated to one component.

I hope so, the problem is that I'm continueing to drive the vehicle though. I've turned the boost all the way down but I need the car to get to and from work. Hmmm, I hope that no little bits of metal make it into my 16G, that would really make me blow my lid!

Hm, maybe time to upgrade the pistons? Fueling, I bet, was the issue.

Well, I'm almost positive when it happened. Right before my car broke down I was driving home from work and I had a really loud backfire (as in back through the TB

) and the car broke down just after that. When it happened I wasn't even on boost, I was cruising at about 70 mph. The cause was the O2 sensor wiring that we had recently rewired to try to get my O2 sensor working. I think that when it shorted it caused an extremely lean (or possibly rich I guess but that seems unlikely) condition in #4 and she let go.

How long before you take the engine apart and what are you going to use in the meantime?

Steve

I don't really know when I'll get to tearing it down. I'm ass broke and don't have a garage to do it in. I don't want to do it in my carport because it's open to the elements. I'd like to just do an engine swap and then take my time rebuilding my engine down in my basement or something. That way I could do it right, custom pistons and rods, maybe even a stroker kit to make it a 2.4L, stainless head gaskets, head work (port and polish and a valve job) or maybe even DOHC heads. Port the intake manifold and TB and go with at least a STI top mount. Ya know, the little things.

In terms of a car, I might get a Mazda 626 from Vikash but the wife is battling me on it. She want's me to just keep driving the car until we have the money to fix it but she doesn't understand that I'm probably causing more damage everytime I drive it! I really don't know what I'm going to do. If I could get an EJ22T short block at a reasonable price I could probably get it done in a weekend. Problem with that is that I really need to do my clutch too and my engine and tranny mounts need done as well. The price just keeps going up and up. If I could just get a good job it would solve a lot of problems.

On a happy note, it was really good to finally meet Ben, Sam and Dave in person. It was a lot of fun, especially the drive down. That was one long ass line of Subies!

Ben got a ride down the 1/4 mile in my car and it was a fun run, even though my car was doggin' on 3 cyclinders.

I will say that it is amazing how well the EJ22T does on only 3 cylinders. Crazy stuff. If I could have kept my intercooler inlet hose from blowing off I believe I could have had a couple runs in the 14's even on the fubar-ed engine! That's sayin' something.

boostjunkie · Post by **boostjunkie** » Tue Sep 21, 2004 3:37 pm

Matt, I'm sorry to hear about your issues with the car. As far as engines go, I might be able to check out the local Crazy Rays sometime to see if they have any turbo legacys in the yard. They get them in at random times.

legacy92ej22t · Post by **legacy92ej22t** » Tue Sep 21, 2004 3:42 pm

Thanks Jason. I'm not sure if that is the same place that Phil was talking about or not but he said he thinks he knows a yard down there that may have one too. If they do and the price isn't too bad a may be very interested.

I'm not sure how I would get down there to get it though.

boostjunkie · Post by **boostjunkie** » Tue Sep 21, 2004 4:02 pm

I'm pretty sure it's the same yard. They actually have two. One in Jessup and the other in Baltimore. I can take a look. No biggie. Only $1 to get in. Their engines typically run around $150 or so

The only problem is that you're not sure what you'll be getting.

I posted a link to a bunch of recyclers that have turbo legacy engines in stock. It's in the engine forum under the "bottom end gone," or something like that.

professor · Post by **professor** » Tue Sep 21, 2004 4:43 pm

Feel free to hurl abuse my way if this makes no sense...

If you used a MAF from something like a late 80's Corvette, it throws a 0-5V signal (as do many Robert Bosch MAF sensors). The airflow would obviously be much higher for any signal level. I'm sure the exact figures could be found. The stock ECU can use that signal, but thinks the air flow is much lower. It outputs a duty cycle to the injectors.

If the injectors were proportionately larger than stock (maybe a necessity anyway at higher boost), they would pump out more gas than stock for any given signal.

The key would be to find a MAF, and an injector / fuel pressure combo that scales things up in the same proportion. I'm sure some bolt-on kits do just that (don't they ? ).

The key here is that once figured out, it could represent an easy and inexpensive mod with lots of spares out there for cheap. Maybe I'm stating the obvious, but the key is that with the right swaps, there may be no need to re-map the ECU, spend big bucks for a programmable ECU, or build bench-top "signal translators", all of which sound time-consuming and perhaps unreliable.

The system could be fine-tuned by adjusting fuel pressure to hone in on air-fuel ratio.

vrg3 · Post by **vrg3** » Tue Sep 21, 2004 5:01 pm

professor - What you're describing is a lot like using an AFC to "control" larger-than-stock injectors. The issue I have with that is that it throws load computations off, and so you end up with incorrect ignition timing. The only way to make it safe enough, I think, would be to make the whole setup run overly rich in order to stave off detonation.

A lot of people used to do something similar when turbocharging early EFI engines. You just put big injectors on and then stiffen the spring in the flapper-door airflow meter. These engines didn't typically have ECU-controlled ignition though.

I think it might also be kind of what Perrin does with their BigMAF kit for the WRX. I might be wrong, but I think you use Perrin bigger-than-stock injectors with a Perrin MAF housing that has a larger cross-sectional diameter. You get better flow, higher capacity, and more advanced timing, I guess.

If you were going to try this route, you could get injectors that don't quite flow enough and then fine-tune it by increasing fuel pressure little by little. Increasing the preload on the FPR spring by crushing the cap in a little is one way to do that.

Matt - She doesn't want you to take a free car that can get you around even if Subarina breaks down (which will eventually happen if you keep driving her indefinitely)? Honestly I don't see the logic... Or does she just not want you to take the time to come to get it?

BAC5.2 · Post by **BAC5.2** » Tue Sep 21, 2004 5:26 pm

The yard I was talking about was Crazy Rays. They HAD a 92 turbo (I know, I took the ECU and tail lights) there, with 186,000 miles. The body panels looked good, so it was there for a reason. Might have been tranny failure (4EAT).

They charge $150 without accessories.

You should be able to fit a long block in the trunk of Subarina. You could install your stock turbo, and run conservatively while rebuilding your engine.

I already spoke to my mom about the future of my car, and if/when something lets go, I'm just gonna shop the car and rebuild the engine over a summer.

Tleg93 · Post by **Tleg93** » Tue Sep 21, 2004 6:46 pm

legacy92ej22t wrote:Thanks Jason. I'm not sure if that is the same place that Phil was talking about or not but he said he thinks he knows a yard down there that may have one too. If they do and the price isn't too bad a may be very interested. I'm not sure how I would get down there to get it though.

What about the guy who works at AR Kinley? Last time we spoke he had two turbo blocks sitting in his garage.

georryan · Post by **georryan** » Wed Sep 22, 2004 3:18 am

I just thought of something...

THe stock ecu maxes out the pump after it sees 12.?? psi of boost right? So, on the stock turbo, will a walbrow be pushing more fuel than you want to run at 13 psi?

BAC5.2 · Post by **BAC5.2** » Wed Sep 22, 2004 3:19 am

Fuel pressure is controlled by the fuel pressure regulator.

The fuel pump just fuels as much as the FPR allows.

vrg3 · Post by **vrg3** » Wed Sep 22, 2004 3:28 am

Kind of.

The fuel pump just flows as much as it can all the time. If working correctly it is always flowing much more than the engine can use anyway. The FPR and injectors work together to meter how much fuel gets into the engine, and those things will still work with a higher-flow pump.

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3rd Annual Subaru Shootout: Recap: MAF discussion