Down on power- bottom end refresh?

#1

The Story begins…

I had a great time at NJMP this weekend. I walked away thinking I have alot to do on the nut behind the wheel and I still do. I was 4-5 sec behind the leader.

After watching some video of other drivers i am really convincing myself that I was really down on power. coming thru the Esses others are shifting 3rd to 4th maybe 10 Ft sooner than me, but they are shifting to 5th at the beginning of the straight. I am not getting 5th at all. Even if i was really bad coming out of the octopus. i would hope to hit 5th by the turn 1 breaking zone.

I still need to make sure i have the right diff in the car.

But I did a compression test last night. I stopped after 3 cylinders
all 3 were reading 130 cold dry and 150 cold wet :frowning:

that is so low i couldn’t believe it. I ordered a new compression tester just so I could double check. I also ordered a leak down tester. The car runs fine. doesn’t burn any oil. I had a few misses mostly due to low fuel(i think). More results to come this weekend.

History of this engine:
I over heated this at NHMS due to a failed motor mount. I ran a full 1.5 laps with the dash temp pegged at max. I now have bright LED lights that warn of temp and pressure loss.
It seemed to run fine after that, but i soon found that It was pressurizing the coolant and over heating.
Warped head- Took it off complete head rebuild by a very reputable shop. new cam, several new rockers, a few new valves.
this is only the 3rd track weekend on this head.

With the new testers I will run the following:
Compression Cold and Warm, Dry and Wet.
I will also do leak down tests.

If compression stays low/leak down is greater than 5%, then I guess I am pulling out that bad boy for some bottom end work.

#2

It’s hard to get absolute #'s out of a compression test. The test works better for relative #'s. I would test the rest of your cylinders with careful attention to battery charging and engine temp. See if you have an outlyer or two.

With my compression tester I always get low #'s just like you got.

If the compression test doesn’t clearly show a cylinder or two down, consider doing a dyno test with some other SpecE30 types in order to see what kind of #'s your engine gets vs. there’s.

#3

Do a leakdown to see where the problems are. If you overheated you have probably compromised your rings.
This test will show if it is the rings or head. Note no horsepower is made below the head gasket:woohoo:

#4

I ran some Compression tests and here are the numbers with my new tester:

Cold Compression test:

Cyl# DRY WET

1 - 157 - 170

2 - 155 - 158

3 - 150 - 160

4 - 140 - 150

5 - 150 - 162

6 - 150 - 165

So this tells me there is something wrong in Cylinder 4 and the rings in general?

I also ran a leak down test. cold using 90 PSI

Cyl# Leak %

1 - 1%

2 - 2%

3 - 7%

4 - 9%

5 - 4%

6 - 8% this one gave me very inconstant readings, then it stabilized here.

I also tested the TPS sensor and I am getting the right readings: connected pin 1 to 2 when closed, no connections when partial throttle, connected 2 to 3 when at WOT.

#5

It does not tell you that your rings are bad. They’re not going to be perfect, sure, but “bad” is a strong word. The reason for the parsing is that it’s pretty easy and cheap to do a head fresh if you keep the same moving parts. But if you go after your bottom end mission creep is going to strike and, to your great surprise, it’ll be a $6k engine rebuild by the time you’re done.

If you can R/R the head yourself you could potentially do an 80% solution for <$500. That buys you a headjob, gasket set and tbelt. How many thousands is that other 20% worth to you? IMO it takes about 3hp before you can get the tiniest hint that one car might have more power than another. If the additional power came at a price of $1000/hp, would that be ok?

If you’re lean on cash, I’d suggest doing the head and giving the motor another couple years. Then spring for a complete rebuild. If you’ve plenty of cash, then no worries.

#6

I suspect your power is equal to the front runners. The main difference I see between two of these cars is where the power is applied. 10 feet sooner in a corner will equal quite a bit at the end of a long straight, enough to be the difference between 4th and 5th gears. Work on the driver first!!

#7

Just posting an update:

Not sure if it is a the fix or not, but I was replacing my injectors this weekend and noticed that i was missing 3 of the 6 Pintile caps off the old injectors.

I thought they had fallen off just at i removed them, I searchd but could not find them in the intake or combustion chambers.

My car was ~75 lbs over weight last year but now I should need to add ballast to make weight.