Jun 6, 2013 update to the Subaru Impreza WRX project car

Inspecting the Injectors

Our WRX is still under the knife... or wrench. The engine teardown revealed many problems, and we're looking for the source.
Dirty injectors were an unlikely possibility, but with 200,000 miles on them, they deserved a good cleaning anyway.
They came back clean and good as new. According to the sheet they sent us, there was less than 2 percent difference in flow across all four—after the cleaning, of course.

Having discovered cracked heads, burned and cracked valves, hammered bearings and a bent crankshaft, we determined pretty quickly that this car saw some serious detonation in addition to the oil starvation. This is likely because the car ran lean.

But how? Mach V Motorsports stands by their tune. They’ve run many cars in a similar state and never had issues. So we started looking for mechanical problems.

First on the list: fuel injectors. This was unlikely since the exhaust valves were burned on every cylinder and both heads had plenty of cracks. Whatever the problem was, it wasn’t local to one cylinder. The odds of every injector getting clogged at once are slim.

That said, this is a 200,000-mile engine running on its original injectors, so we had to check ‘em out at least. A professional injector cleaning is a must for any high-mileage car. We took ours out and sent them over to Marren Fuel Injection.

When we got them back, the tests showed about what we expected: They were a little old and didn’t flow perfectly, but they weren’t bad enough to cause problems. And, after Marren cleaned ‘em up, they flowed like new.

We’ll have to keep looking.

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Alan Cesar
Alan Cesar Dork
6/6/13 10:22 a.m.

Having discovered cracked heads, burned and cracked valves, hammered bearings and a bent crankshaft, we determined pretty quickly that this car saw some serious detonation in addition to the oil starvation. This is likely because the car ran lean.

But how? Mach V Motorsports stands by their tune. They've run many cars in a similar state and never had issues. So we started looking for mechanical problems.

First on the list: fuel injectors. This was unlikely since the exhaust valves were burned on every cylinder and both heads had plenty of cracks. Whatever the problem was, it wasn't local to one cylinder. The odds of every injector getting clogged at once are slim.

That said, this is a 200,000-mile engine running on its original injectors, so we had to check 'em out at least. A professional injector cleaning is a must for any high-mileage car. We took ours out and sent them over to Marren Fuel Injection.

When we got them back, the tests showed about what we expected: They were a little old and didn't flow perfectly, but they weren't bad enough to cause problems. And, after Marren cleaned 'em up, they flowed like new.

We'll have to keep looking.

Wicked awesome Scooby Rexes in your treeware mailbox. Subscribe to Grassroots Motorsports now.
Alan Cesar
Alan Cesar Dork
6/6/13 11:07 a.m.

We're pretty sure what the problem is. We'll reveal it in an upcoming update.

Gearhead_42
Gearhead_42 Dork
6/6/13 1:41 p.m.

Tell you what though, after having 2 clogged injectors cost us a fresh motor (and a whole race weekend) the first thing I do with any new project is send the injectors out to be cleaned and flow tested...

bstuke
bstuke New Reader
6/6/13 3:32 p.m.

Awesome stuff guys. I am getting the first 818R. Can't wait to have it running!

mhisstc
mhisstc New Reader
6/6/13 4:15 p.m.

We heeded another racer's recommendation when we built the Cobra engine for our NASA CMC series fox Mustang, and without question sent our used injectors to Marren to be cleaned, checked, and flow matched for less than the cost of new ones. We had a few spares, so we sent them along just in case. I'm glad we did. Marren determined one of them was bad. That would have been "heck" to try and troubleshoot on a new engine. The spec sheets they send back with each injector are fantastic information to have for piece of mind if nothing else.

David S. Wallens
David S. Wallens Editorial Director
6/6/13 6:28 p.m.

Plus Mr. and Mrs. Marren are nice people.

jmr302
jmr302 New Reader
6/8/13 2:45 p.m.

Was it a worn out MAF sensor? That happened to my '02 WRX. It wasn't diagnosed until the new engine was being dyno tuned by a professional just recently.

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