Weak Dyno and Compression Tests; What now??

#1

[attachment=1782]e30Dyno02.06.12.jpg[/attachment]
So, I suspected low power after racing in December.
A dyno run in February (plot attached) showed max power at 143 HP at 5300 RPM and max torque at 146. (Also running lean) Not good; confirms my suspicions about low power.

[attachment=1783]e30Dyno02.06.12_2012-02-25.jpg[/attachment]

So, the next move was a dry compression test with a warm engine. Results for cylinders 1 through 6: 136, 126, 103, 137, 140, 140. This indicates that cylinders 2 and 3 (at least) have a problem.
Third test was a leak-down test with a warm engine. This is tricky to get consistent results, and I tested each cylinder at least twice. All cylinders indicated ring leakage (hissing noise in the dip stick tube). The net results for each cylinder were:
1 - 40% leakage, no valve leakage
2 - 55% leakage, exhaust valve leakage
3 - 50% leakage, exhaust valve leakage
4 - 40% leakage, exhaust valve leakage
5 - 100% leakage, exhaust valve leakage (sticky valve?)
6 - 40% leakage, exhaust valve leakage

Now some history; this was a refreshed engine installed in April 2009. In summer 2009, due to a coolant hose blowout, the engine overheated, but continued to run OK. No signs of head gasket leaking or crack in head. (no milkshaky oil). I raced this engine in '09, '10, and '11. The only issues were two broken rocker arms.

Please help with these questions:
What does the dyno chart tell you?
Given the compression test info, will a new head/gaskets fix this?
Or is there evidence that the rings are leaking too much also?
Suggestions for other tests before jumping into the fixes and replacements?

Clearly, I’d rather just replace the head. But I don’t want to go to the trouble if the result is a good top end on a weak bottom.

Thanks for the help! Jon

#2

The A/F ratio in the dyno data says to me that the engine is running right (for a street car) and is holding 14:1. The compression and leak down results suggest that the rings are shot, probably from the overheat. But the compression and leak down results are somewhat at odds. Compression results say that cylinders 2 & 3 are the worst, but the leak down test says that cylinder 5 is the worst. That makes me suspect the validity of the leak down test. But if even close to being correct the leak down numbers point to bad rings.

Try a wet compression and leak down test and what that says. If the rings are the problem a wet test should result in better numbers.

#3

+1 for what Jim said. The only question that really remains is whether you might sneak by with just doing a top end refresh. Which, judging from the evidence so far, is unlikely. If your wet compression and leakdown tests turn out pretty good, that will confirm the your bottem end is shot.

That may seem contradictory, but the wet test seals the rings, so if wet results are better than dry results, the rings aren’t sealing.

You’re in Atl right? Chuck Baader is in Montgomery.

#4

Did Chuck move from Birmingham?

#5

Oops, my bust. I meant Birmingham.

#6

40% leakdown would not represent a 143hp engine. The compression shows and issue, but it appears you may have not done the leakdown test correctly.

You should do it cold, and then hot to see the difference. If you are building a race engine, more than 2-3% leakdown across the board when hot is cause for rebuild.

#7

These motors are not tolerant of overheating. I also suspect the leak down (did you insure that each cylinder was at TDC?) was done incorrectly. However, the compression numbers definitely show a 145hp motor. Can you freshen the head? Yes, and pick up nothing, and probably cause more problems. Your major problem is in the rings and you need a complete rebuild. Chuck (in Birmingham):laugh:

#8

Thanks for all the good feedback.
The leakdown testing was done with the valve cover off so I could see the cam action. I listened to the tube connected into the spark plug hole (stuck it in my left ear) for the cylinder to stop ‘exhaling’ on the upstroke. I stopped rotation at the end of exhale and used that as TDC. Correct?

Also in the leakdown test, when the compressed air was connected to the 5 cylinder, the engine rotated a few degrees and 100% leak was detected. (I suspect this indicates an intake valve stuck open the air migrating to other cylinders, causing enough pressure to rotate the engine. Once the rotation occurred - test on #5 was invalid.

I did a wet compression test with a cool engine. here are results:
1 - 160, 2-155, 3-140, 4-160, 5&6 were inconclusive (the test gauge would not hold a reading:huh:)
So, each of the cylinders 1 to 4 improved significantly with the wet test. This indicates a bunch of bad rings, correct?

Anybody got a good engine available?

Thanks again for the good input.

#9

When I do a leak down test I just rotate the engine until both cam lobes on the cylinder are down. Just like you’d do when adjusting the valves.

The wet compression test does suggest worn or damaged rings.

If you want to come get it I have what should be a pretty good engine. It came out of the 96 car after the wreck. It was a 120k engine when I put it in the car and saw one year of racing. The one time I had it on the dyno it made 154hp. It has a new oil pump and IJ scraper. You can have it for $500.

#10

That car for sale at Ft. Stewart is supposed to have a rebuilt bottom end. The seller says that his mechanic said it had an “out of round cam” IIRC. I don’t know wtf that is supposed to mean, but it’s possible that the mechanic is full of shit and the whole engine is good. you could get the whole car and sell enough parts to pay for it and the gas to fetch it, keeping the engine for yourself.

Give Brasseler an upgrade frome 10Meg to 50Meg for a year and I’ll buy the car for you and help you swap the engine.

For those that don’t know it, Jon is a TelCo guy.

#11

Good idea. I’ve sent a note to the Ft. Stewart seller.
I’d like to find an engine in a car, so I can do a compression test before buying. Maybe even a dyno. The last thing I need is another 143 hp unit.

Probably can’t get Brasseler the bandwidth upgrade; but perhaps other forms of bribery?:wink:

#12

Thanks, Jim. I’ll send you a PM for more info.

#13

[quote=“alfageorgia” post=63670]Good idea. I’ve sent a note to the Ft. Stewart seller.
I’d like to find an engine in a car, so I can do a compression test before buying. Maybe even a dyno. The last thing I need is another 143 hp unit.

Probably can’t get Brasseler the bandwidth upgrade; but perhaps other forms of bribery?;)[/quote]

Don’t overestimate the difficulty in this. Your proximity to Chuck Baader is a significant issue. You could take your car to him and leave it there. Then pick it up a month later with it’s rebuilt engine installed for 1/2 the price you’ll find else where. Or you could help him with the R/R of the engine and learn a lot. I’ve swapped a lot of engines but I’m bush league compare to Chuck.

Alternately, I have a Chuck Baader bottom end wrapped in plastic in my garage that I probably don’t need. It’s .020 over and has only a couple weekends on it. I’d have to go thru some old notes to figure out how much I have in it, but it’s likely to be approach $2k. An .020 over build means new pistons and they are pricey.

#14

Man my motor only made 146 hp with good compression, and that was before I overheated it at Nashville last year. I guess we will see how it does this weekend, and then I will decide if I am in the same boat as you.

#15

I know the goober that assembled the engine. It was a hone/stock pistons with gap-less rings from Total Seal.

I’m not an engine guy, but I’m of the same opinion as the others, the rings lost compression in the overheat. Perhaps some scoring in a cylinder wall or two.

Buy the Levie engine. The crank scraper is worth $200 and it was good when it was pulled out of his car.The 154hp #s mirror everythig that I’ve been getting from my shadetree rebuilds and they cost about $2000 just for the refresh-type parts. Do a clean-up and transplant it into your car. Take the time to do a head-off inspection of the “hot/heated engine” and report your results to us.Perhaps leave it with Chuck for a future rebuild/spare engine?

We’re learning too many expensive lessions, but it look like tis one will only cost $500.

RP

#16

The Ft. Stewart car is a no go - the engine is not right for us.
I’ll probably go with Levie’s engine - he’s going to do a leak down to verify it’s ok. Then the big drive to Huntsville and swap-a-roni. Anyone want a tired engine that needs a rebuild? (I’d love to tackle this, but being realistic it might get done by June 2016.)

#17

I would be interested in helping you and Levie with the engine swap since I haven’t done one.

#18

Would anyone be willing to post a good dyno plot for a Spec E30 motor (recently rebuilt or whatever). I’d like to see what is ideal. Thanks!

#19

Do a search and you should be able to find an older trend by Carter listing dyno plots and there is also one from all the dyno runs at last year’s Nationals.