ohjonnybomb

OK, long story short,..
Last summer I put big bucks into my 93 Eng rebuild
-3 MM
-New housings
-Street Ports
-Single 3574 turbo
-1600's
-blablabla

I was never happy with my hp#'s after break-in (370whp at 15lbs)
It would break up a bit up top.
There was gas coming out from around one of the injectors.
On some pulls giant plumes of smoke came out the tailpipe.
The builder said this was all normal and my #'s were normal. ??
I drove away, and saw knock readings on the PFC at 100.
I called the builder from 4 miles down the road to report the high knock.
He said,.. "Its been tuned. Its fine. Drive it and have fun."
His lack of surprise or concern, tells me he saw these high numbers during the all day tune.

In the next 1000 miles I did some highway pulls, no races. It felt good but not what i expected. Then I started to notice lobeing idle and low vacuum after I would get on it. Sometimes it would clear up, but hot starts were very hard, even impossible. I have a small relocated battery, so it is not getting hot.
Idle Vacuum was down into the 300's then the 200's and the rpms would fall low too.
I have a simple compression tester and saw 60,60,60ish on one rotor.
I was convinced it must be shot, so I pulled the motor myself.
Question
- Once its out, is there a way to tell if the motor really is bad?
- Does it sound like I did the right thing?

surfmon

iTrader: (6)

that was the short version??

1)pull it apart to know for sure

2)yes, better to pull it apart now then wait until it completely grenades on you

t

Mahjik

iTrader: (1)

Before you pull it apart, pull off the turbo and manifold. Peer into the exhaust port on the housing which is reporting low compression and take a peak at each apex seal (i.e. turn the shaft to see each one).

afterburn27

iTrader: (5)

It doesn't sound good, but I would definitely check the condition of the seals through the exhaust port like Mahjik posted.

Gas coming out around one of the injectors is not normal, it was not seated correctly and was leaking under boost.

BTW, what turbine housing A/R were you running?

Did you have a wideband AFR gauge hooked up?

ohjonnybomb

Yes good idea, I did peek into the exh ports expecting to see some kind of damage. Nothing obivious, all Apex seals are intact, no scratches on the inside of the housings.
I did notice some major variation in the ease of movement of the apex seals.
the front rotor seals require substantial finger pressure to compress them ageinst their springs. Two of the three in the rear rotor are less firm, but close. The third is very soft. As oilly as it is, I can even slide it back and forth from tip to tip. It slides what looks like an 1/8in.

There was a AFR gauge hooked up for the dyno tune, Ill have to check what it was tuned to, but I remember it was supposed to be on the safe side. 11.2? Ill check that, and the turbo specs. I always went with builders recommendations.

GoodfellaFD3S

iTrader: (213)

The builder said gas coming out from one of your injectors was normal??

Motor sounds shot to me. Could be that your OMP is dead, leading to lack of lubrication. One possibility........

Dudemaaanownsanrx7

iTrader: (23)

is it possible that the compression readings are only low cause the injector is not allowing the compression to seal? what were the compression readings on the other rotor?

rossc

Eh? Unfortunately the injectors arn't related to compression. Fuel injection happens prior to the compression cycle. The only things compression can leak past are the spark plug holes, or the seals.

It sounds like you had a shop with a bunch of lazy mechanics.

Dudemaaanownsanrx7

iTrader: (23)

Oh thats true. I didn't even think about the injectors being in a different area then where the combustion takes place. OP did you check the compression right after the rebuild?

Mahjik

iTrader: (1)

Ok, I guess the next question is, are you planning to have the original shop address the issue or not?

The reason I ask is that if you are. do not take the motor apart. If you are going to have the original shop address the problem, get the engine to them intact and let them crack it open. If you are just going to address it on your own (i.e. do your own rebuild or send it somewhere else to have a rebuild), go ahead and open it to find the damage.

If you have very low but even compression on front or rear, that usually means rotor housing damage (as that would be the common part for all three apex seals).

ohjonnybomb

Mmmm, Im not happy.
"ignore the knock reading, its tuned"
That line haunts me.
But I want to be fair, and I dont know what is wrong yet.
Is there a way to test compression with the engine out? (tranny is in the car)
If I crank by hand?
Or is that not fast enough?
Surely someone must have cranked a good engine by hand and got a ballpark number?
How about that soft apex seal, is that a Big Red Flag, or nothing at all?

Mahjik

iTrader: (1)

You aren't going to get a useful reading turning by hand. The best you can do is listen to hear if you are making "any" compression when turning by hand.

If you aren't going to send it back and try to make a claim with the original shop, then I would go ahead and crack it open as that's the only way you'll know what's going on. If you are going to make a claim with the original shop, just get it back to them immediately.

pp13bnos

iTrader: (1)

High knock can be caused from the exhaust pipe hitting part of the car. This happened to me. CJ

grimple1

iTrader: (1)

yeah, knock can be really almost anything. some engines/cars are more noisier than others. We just had a good discussion about knock in chuck's pfc newsgroup.

if the engine is out and you're doing the rebuild yourself then you might as well go ahead and start the process. it'll be very difficult to turn that thing by hand and get any real numbers. BUT why does it mattter. I thought you already ran a compression test before yanking it.

ohjonnybomb

Your right, and it said 60.
I expected to see an apex seal screwed up. When I didnt, I second guessed myself,.. or my compression gauge and wanted to double check, if possible, before I went further. I guess the next step is to buy a 54mm socket? lol
maybe a side seal or corner seal?

Rotors R Cool

I talked to Rotary Performance about knock since my readings are always around 60-65. They basically told me that all motors have different "background noise levels" meaning different noises made by parts of the car that the knock sensor thinks is knock. So, bad knock readings are really relative to the car itself. If the background noise is 20, then the dangerous readings are like 80, if the background noise is 60, then the dangerous readings are like 120...

Rotary Performance also told me that I might as well not even look at the knock readings because in most cases, a real knock on a rotary ends up in a rebuild.