JK5S

iTrader: (2)

Here it is guys I need your opinion. When I compression checked the car it measured 60 psi consistently on every bounce on each rotor.

This engine is pieced together out of FD twin turbo housings with RX8 rotating assemblies (rotors & crankshaft and seals). The engine is NA.

I've removed the exhaust manifold and manually pushed each apex seal and it was springy consistently across all seals.

JK5S

iTrader: (2)

bump

3vil

iTrader: (4)

how many miles since you put it all together (has it had time to break in and get a good seal)?

JK5S

iTrader: (2)

its got like 250 miles on the motor

bumpstart

my feelings are you have a very consistant pulse on all faces ( good news )
and it maybe just method, or equipment that is the cause for the low reading


did you test from trailing plug with a strong battery and earth with the throttle wide open?

did you let the shrader go and let it pump to a peak value
( it often goes higher when the valve is released , you should use the shrader in method to count pulses and shrader out method to find the peak pressure )

if you did this on a rotary engine compression tester you may find its up a bit higher than with an unknown potentially dodgy pressure gauge
- this is because the pressure transducer sees the combustion pressure without the pressure drop of hose and shrader valve restriction in the way
( and is also compensated on a chart against RPM if you use a mazda tester )

2slow4stock

iTrader: (18)

What did you check your compression with.?

BomberMan

iTrader: (4)

I didn't think 60 psi on each rotor face to be low, in fact I think that is quite high. Or are you talking about 60 psi on each rotor as a whole? Make sure you're doing the test right. Or rather don't do it at all. Unless your engine was built with brand new housings, you can expect to have relatively low compression until the break-in is near complete, so I wouldn't even bother compression testing for awhile unless the engine can't be started.

K-Tune

iTrader: (26)

Why do you think your engine is bad?

JK5S

iTrader: (2)

I used a SEARS compression tester and removed the little valve at the bottom.
I was reading 3 equal bounces of 60 psi of the trailing spark plug holes on both rotors.

JK5S

iTrader: (2)

It got flooded and its hard to start.

JK5S

iTrader: (2)

Each bounce, not as a whole.

JK5S

iTrader: (2)

I'm currently in a middle of taring the intake and vacuum system apart and replacing all hoses and gaskets.
The problem is during starting it is hard to get it to work without the motor just simply shutting off even with the pedal depressed 1/4. When warmed up it runs fine.

bumpstart

sounds like the issue is actually in the tune or in the temp sender or simply crapped plugs
( and a little disclaimer as to potential for a coolant leak issue )

cold compression is usually higher than hot ,,
( argue that all you like , then go and test one ! )

and hot starting OK is a great sign the engine is fine but the cold tune sucks
( again a small disclaimer for coolant seal issues )

i think you need a CO litmus test and a leakdown pressure test of your coolant system to rule out the engine being coolant flooded when cold

you then need check the cold signal from the thermo sender
and then to retune any aftermarket ECU in the cold running and crank maps
and an injector clean and check also wouldnt go as wasted money

K-Tune

iTrader: (26)

Sounds like you are grasping at straws... Considering the compression numbers and age of the build it's doubtful that the motor is mechanically flawed. It's more likely a problem with your fuel/timing.

JK5S

iTrader: (2)

I have the injectors out and will be cleaning the fuel injectors.
What do you mean with retune of the aftermarket ECU, I have none.

bumpstart

well, since you didnt state in the OP that you had aftermarket ECU or not , i put that in to cover all bases

if you are stock ECU,, ( s4 or s5??? ) you have some scope to trim the mixtures at the AFM ( s5 ) or at the trim pot beside it ( s4 )
but to me its sounding like perhaps a leaky injector or a suss coolant sender or as hinting, coolant leak

BomberMan

iTrader: (4)

Or... it could just be that this guy has a new engine that will run like **** until it is properly broken in. I mean seriously, he said it only has 250 miles on it.

If it was me, and I was scared, I would get an AFR gauge to make sure I didn't run lean and just DRIVE IT a lot. Trying to diagnose fuel system problems by the effects you see on an engine that hasn't been broken in, is like trying to get surgery instructions on a cell phone with bad reception. You could guess what it is that you need to do, or you could wait and try to get a better signal.

Hazard15301

iTrader: (5)

Yea doesn't a rebuild need a minimum of 500 miles on it to be considered properly broken in?

I know when I rebuilt my first engine, it was very hard to start, but gradually got better as the seals wore in place.

I recall that it depends on what all you reuse in the build too.

kgracom

That sounds a lot like the problem I have. I found the majority of it was coming from a faulty tps. There was also a bad coil but I would check out the tps man.

JK5S

iTrader: (2)

Thanks you guys, I will keep you posted on my diagnostics once the intake system has been resembled. Anyone know where I can find a intake manifold gasket set for a good price?

JK5S

iTrader: (2)

Do you guys think I would need one of these for making the engine operate properly? Currently I have racing beat headers on the engine so its not like it will benefit me one bit to have it. The intake manifold is plunged in that the area where ACV typically sits.

bumpstart

nope, ACV and EGR if faulty can bring its own problems, leave it off

JK5S

iTrader: (2)

So I understand a unplugged/faulty termo sensor could cause a majority of hard starting. Causes the ecu to go to its basic fuel map and not account for cold starting.

MadScience_7

Don't forget altitude correction. I don't know what altitude SLC is at, but for me in Denver, 60PSI fits close to the correction factor in the FSM. I've been having the same problem, but I've just put in a fuel cut switch and accepted that it won't work right until I can get an aftermarket ECU. The RTek doesn't support adjusting the cranking mixture for S4 N/A though, so I'll have to save up for a year or so to get a real standalone.

JK5S

iTrader: (2)

You are about 1000 feet higher than SLC , so there is something to be said about altitude differential. So, what does your fuel cutout switch do for you?