13B-RE E6X extremely hard HOT start problem
 

Guys,

Engine is a 13B-RE with large streetport, 3mm seals, etc. Running 850cc primaries and 1600cc secondaries (not that it matters for this case).

Car starts beautifully when cold...3 cranks then it fires. However, when hot (85-90*C), I sometimes have to hold the starter down for 5-10+ seconds to finally get it to catch. I have fuel pressure during this time. I've tried adjusting the priming table to extremes (way up and way down) and it appears to make no difference as I'm trying to start it. Once it does start, it idles beautifully at 1200rpm @ 14.7:1 afr.

Any ideas? Map is attached.

My guess its pretty lean. 14.7 is on the lean side, specially if you have a large street port. Make it richer and see what happens.

I've tried increasing the priming significantly at the appropriate temperature and it doesn't appear to make any difference at all! I'm lost on this one!

try moving the staging bar one bar forward of zero.

unless you have a renesis I call bs on your rotary powered car running good at 14.7-1 at 1200 rpm

AFR fluctuates between about 14.3 and 14.9 at 1200-1300rpm. Doesn't really matter for the sake of the problem though.

What do you mean by moving the staging bar forward of zero? The staging bar is set at 12 currently.

Listen, ported turbo peripheral exhaust port rotaries dont like 14AFR or higher. I didnt mean raise the primer map, this will only dump more fuel on startup, i mean the fuel map it self. What are your AFRs with the engine cold? I bet they are below 13.

The last e6x that I worked on had the map dead spot sitting just in front of the staging bar, so on startup it was staging while cranking leading to real inconsistent starting.

are you reading the afr's off of a narrow band?

I'll give it a shot, but the issue is completely related to startup. The engine doesn't want to start at all when it's hot but starts beautifully cold.

AFR's are off a wideband. It's literally like the car has a blown seal when it's hot, but the engine is a fairly fresh rebuild and just performed very nicely on the dyno last week, so no reason to suspect that the engine is bad.

So when actually did the hard starting begin?
Was it doing this even before the dyno tune?

BTW.
Your 14:7 AFR at idle is due to the lack of exhaust flow at idle rpm's. This happens a lot with widebands especially when they are placed further down the exhaust system. Pre-renesis rotaries can't idle that lean with a smooth idle.

What kind of 3mm seals are you using?


-Ted

Check compression. And what are your AFRs at Idle when the engine is cold, ie., you just started it/ambient temp?

When I first got the car running, it had the same hard starting problem. I played around with the priming map a little and it seemed to get better.

Then recently, after the dyno and tuning, it appears to be much worse. It's unusual because we would shut the car down frequently at the dyno and restart it without ever having this problem.

I'm not sure exactly which 3mm seals are in there (I didn't build the engine myself) - why? Is this symptomatic of a specific brand?

Another thing to watch out for is fuel quality? what kind of fuel are you using? is your fuel filter new or old? are your fuel injectors cleaned and balanced? my first "requirement" when doing an install or tune is that the injectors be sent out to get cleaned and balanced with new microfilters so that they will not hinder performance and cause problems just like the one you're having. Is your fuel tank original? it might be very dirty and in need of cleaning. I have seen this countless times.

Also, just to be sure, did you check compression? You should do this first to discard a bad engine.

I'll have to check the fuel filter again, but it's literally brand new. It's possible that during the put together a bunch of shit flew into the tank (this is in an RX8 so it has an extremely unusual fuel tank configuration) and has clogged the filter. But if the filter was clogged, wouldn't that affect cold starting as well? Fuel injectors are new, but not cleaned and balanced. Essentially, everything is new (including the pump). Fuel is standard California 91 octane.

The problem is very closely tied to engine temperature specifically. I'll have to check compression but I literally just finished breaking in the motor and would be stunned if this were the problem!

is this the GRAY rx8 that dave put together

Nope, Dave had nothing to do with this one, although I did talk to him periodically during the build.

I'm kind of supprised that there is more than one RX8 with a cosmo swap in SOCAL

You are? There's pretty much every combination of import car that exists in Socal :)

The seals could be warping when the engine heats up.
Compression is higher when the engine is colder - this would explain why the engine fires up when cold.

Like Claudio mentioned - do a compression check, especially after you get the engine fully warmed up.



-Ted

you sure it isn't flooding due to a leaky injector... do you premix your fuel?

It's premixed...I'll have to check compression when hot.

did you ever get this problem solved thetech?

Kind of...if I hold the throttle approximately 50% during cranking it starts right up after about the 4th crank. Haven't had time to really investigate why that is, but it's liveable for now!

I got the same problem where I have to hold the throttle down about 20% to get it to start...

I also have 3mm seals.. dont know what make it is.. ??? ....

Also it does it cold or hot .. Motor was rebuild 4 moths ago.. :-(...