Often the 3mm seals result in lower compression #'s..the seals are heavier and don't seal as well at low rpm's. Not an issue at higher RPM's as the dynamic compression is always higher.

Surprised they did the 3mm seals...there are issues with some rotors not having enough meat due to the casting differences in the Renesis rotors

Side seals are stock...not sure that anyone makes them except Mazda. No real reason too...they work fine

There has been some talk about the full height seals and the corner seals when converting the Renesis. I would phone and talk to Cam for sure and see what he suggests

 

I understand my compression is low, but I need to confirm as I really don't see how both front and rear can be low at 3K miles. If something broke then I could understand one or the other but not both being so similar.

 

I've heard this as well and suspect my engine(with full height seals) has lower than optimum compression as well . It does seem to be getting better and better over time though - now at 15000kms .

 

Basically what I meant was that might be what you get when you test the compression.....it isn't necessarily a problem if it starts properly and runs....there are big differences in compression and vac results depending on the porting and the seal specs. I had a BPort REW that we built...started up right away and made 500+ HP...but the idle vac was quite low because of the port...

 

All in all I'm just trying to diagnose and fix misfire issue and this was one of those steps that is giving controversial results.

 

1 Piece 3mm?

If so there is your compression loss....

 

I believe 1 piece but am not entirely sure I will ask on Monday.

Why would compression be lower, if someone could care to evaporate.

 

If they didn't properly clearance the housings to the one piece apex seals you may have some blow by

 

1pc seals are stronger because they don't the small bits on the ends

Thy don't seal as well...especially at the start...as the housings tend to not wear perfectly straight across..and the seals will ride up on the ends and cause a small gap

You could get missfires from this...but at almost 100lbs of compression I would look elsewhere first. Especially with a Renesis with no overlap

 

I've looked almost everywhere else.

Vacuum leaks
Plugs (gap changes .045-.033)
BHR coils
OE coils
Increased dwell
Tune

Only other thing I can think of is to much premix or clogged midepipe (which considering it is less than a year old and only has 6K miles I doubt)

The plugs looked fouled and black whenever I pull them and moist so premix may be an issue.

 

thats some serious premix.... What ratio are you running

 

4-6 Oz per tank

 

Correct, 1 Piece seals will always read lower compression at idle - it is a trade off for higher strength.

 

Unfortunatly I could not find a compression tester with a check valve to hold the pressure but what I can tell it was bouncing up to around 80ish

Did another test on my unit and got the same front rotor 104, 95,103 @272RPM. Rear rotor 91,96,93 @271RPM

Snapped a pick of the plugs. These plugs have less than 1000 miles on them and have less than 500 miles on them since they where pulled and cleaned


Again why is compression done on trailing vs leading? Shouldn't it be the same?

 

Won't make any appreciable difference....both of the plug holes are in the compression stroke part of the rotation.

Not sure why they do it...maybe just because that's what they always do

 

There have been quite a few occurrences of misfires from BHR coils recently . If I were you I'd swap back a set of stock coils on stock Dwel and see what that does .

 

I have already Brett, even got my BHR set replaced with a brand new set and on both sets of BHR and OE I get the issue. Happens above 7K not always but usually when load is 40% or higher AFR is about 12-13.

I'll see what Cam says tomorrow, regardless I have a few more things to check and I am doing a teardown starting this weeks anyways to do some chassis work. So I am going to go over everything again.

 

OK . In that case try doing logs of misfire events to confirm AFRs . Set to log and attempt to recreate the misfire - the instant after it happens shut down the log . Then analyse that particular portion of the log . I wouldn't mind betting it goes super rich at the point of the "misfire" .

 

I have some logs on my other computer where I got misfires, the AFR went slightly irritate but I don't remember seeing anything to drastic. I will siphon threw them again tomorrow and double check.

Side note when I first started all of this my misfire would happen at 4K RPM than slowly as tuning progressed and the engine broke in the misfire moved up to around 7K RPM not sure if thats relevant or not just a weird observation.

Unfortunately not a whole lot of driving can be done right now due to the weather, so most of what I can do is based of what I have seen before I might try switching to Denso plugs, going to send my injectors out for flow testing to see what they are flowing. Double check my injector wiring. Clean my MAF, Clean my ESS, triple check my midpipe. etc...

 

It's a long shot since your engine is so new but you could have your oil tested. I was having similar high RPM misfires on my last engine. After doing all of what you have done (sent BHR coils to charles, swapped on OE coils, tune, etc), I finally sent my oil in for a sample (usual thing for me every few changes) and that is when they found coolant in my oil.

I never noticed a loss of coolant because I caught it early. So I just pulled the engine and sent it to Pineapple even though it was running fine with the exception of the random high RPM misfire and when Rob pulled it apart he found the small failure in the coolant seal. He thought that high RPM the coolant was causing a misfire. Had I not caught it early it would have likely just gotten worse as time went by and ruined the engine completely.

 

I once thought the same thing Scott, when I was getting hard starts and white smoke out of the exhaust.

Hard starts where from a vacuum leak, and I never pin pointed the white smoke it is only present when the car is cold. Once warmed its barely noticeable. I sent oil to blackstone at the time anyways and heres the report. This was at 1300 miles on the rebuild I was going to send in another sample now that I am at 3200 miles and see if their is a difference. But that wont be till after I pull the motor.

 

Well that rules that out. Come to think of it I remember you saying you did that already,

 

I have been very meticulous in trying to hunt this issue down, just unfortunately everything I do shows their should not be a problem when I am getting one.

I am almost out of places to look

 

Spoke with Cam yesterday he said that those numbers do seem a bit lower than he would like to see but not out of what is acceptable. I finally got info on the seals. OE corner and side seals where used and flexforce FD apex seals where used which are two piece. He said those numbers should rise and that if they don't by the time I hit 10K that we will look into it then as they will not cause any drivability issues. The car starts and runs strong. Even without a tune it makes more power over my original motor so I am not to worried about it.

He did reccomend a good grounding kit, header wrap as my IAT on the rear rotor may be saturated (guess a black LIM was not a good idea ) clean and check ESS for deflection.

I am also going to double check my injector wiring, get my injectors flow rated, clean plugs (may try a set of the denso plugs see if that helps), stop premix for a while.

IF anyone else has anymore recommendations I would appreciate it as well. I will also be sending my current oil (2K miles) sample out to blackstone for testing again.

I was a little lazy when I left so I never got around to doing a good detail job, so thats the plan for today and tomorrow and hoping to have it all torn down again by the end of next week.

 

long shot here, recently saw a car that kept suffering random misfires, sometimes at idle, sometimes under load.

Turned out to be a frayed OMP wire, wouldve thought it would have set off a separate CEL, but it just kept randomly misfiring.