zayrx7

Well I pop the motor today, while getting on it I was running about 17psi. I think the cold weather lean it out even though my car was tune @ 10.5 AFR, my pfc show a -1 air intake temp, shift @ 8300rpm,
121 knock. It was a stock motor with a T78 on it, now it time to do a race port with the upgrade T78 wheels. I'm shooting for 600hp this time.

Bridgeported

Are you pretty sure it popped b/c of the cold weather? It can happen, but if you were running an EMS system you also could have tunned in a map to compensate in colder weather conditions.

es

The power FC (pfc) has cold intake air temp fuel enrichment correction factors. Be sure to bump those up so you don't end up in the same place you are now with your next motor.

nocab72

I tuned the car, he was running the same temp correction maps as I have, tTweaked by me for our setups over time in many different temps (ie I drive around with WB in my car all the time, logging as much data as possible, then tweaking constantly [obsessively]).

The timing maps were nearly the same as I used (for months) with my stock motor & GT35/40 setup. Split under higher boost was conservative, Zavier was running 12 when I ran 8 for months and no problems. AFR's were very conservative, like Z said mid 10's.

Zavier drove the car 15 miles after he suspected the engine went (we were on our way to lunch with guests). On the way back from lunch, his orange fuel light came on.

I'm gonna call it as either:

1) fuel line freeze/ or fuel freeze in tank due to such a low fuel level
or
2) a fuel pickup problem with such a low a fuel level

My $0.02

K

Boostn7

nocab: do you monitor knock when tunning?? or disregard it some do....

I've been tunning mine up to 17 psi and with A/Fs in the 11.2-11.4 my knock #s are less then 50.

I drive with my FJO wideband full time too.....

nocab72

Boostn7 - I do monitor the PFC knock closely, although I've found that the "peak" knock on the PFC is worthless since my peak values usually come during non-WOT (either shifting or coasting?!?) that is a whole other thread I started a while ago though and I won't touch it in this one.

But to answer your question, yes, I do. My stock motor was "knocky" with values 40 - 50 during WOT being normal. The new pineapple motor is significantly less "knocky" with values 20 - 30 during WOT being normal. I use "relative" knock numbers for a car, opposed to some hard/set "threshold" number. ie Apexi saying knock > 60 == bad. I've found for some engines, 60 knock is normal, not bad. Now if I had a car that normally knocked 60 during a WOT all of a sudden have consistant 75 knock in specific cells during WOT I would look into that, adjust afr's, timing, etc around those cells and see what was "causing" those higher values.

K

PS Hear you on the WB/FJO all the time. I now feel so naked w/out the OZ-DIY hooked up in my car while driving.

es

Are the spark plugs white?

nocab72

I don't believe they have been pulled yet. But we will post pics once we do. Unfortunately Zavier was not logging when it happened, so it's only post-mordom (sp?) info we have to look at to determine the cause.

K

es

I just split a motor Friday night out of a T-78 with 3mm Hurley apex seals & we found white exhaust ports, light tan plugs & huge dents in the rotors... (as well as 2 cracked side seals & 2 chipped apex seals)

Apparently the boost controller quit controlling boost right around redline, but that's all I know.

nocab72

I have seen the trashed exhaust wheel from Zaviers T78, so we know it spit a seal or two...

K

Bridgeported

WOW! That sounds like some pretty serious damage. I've seen worse, but generally it's not quite as bad as dented rotors, cracked side seals, etc. Try to get pics of the damage. Sorry to hear about it though.

es

I'll try to get a pic of one of the dented rotors tonight (it's sitting in my parts cleaner) as well as pics of my installed Greddy 3-row.

Funny thing was when he showed me the apex seal chunks that were rattling around in the exhaust manifold.

Oh, & I meant to type Corner seals not side seals.

vosko

iTrader: (4)

i'm with boostn7. i have my FJO in my FD all the time....

it sounds like zavier got some air in the system instead of fuel and boom.

i have a sump and ss braided an fuel lines from the sump to engine so that never happens to me.... hopefully

nocab72

With the amount of "squat" and "rock" our cars develop as HP exceeds 350rwhp, no doubt, the importance of not running on fumes becomes greater. This very well may be an example of that.

K

Bridgeported

What exactly do you mean? Do you have a fuel sump installed in your system somewhere between the tank and engine? I'm kinda lost... what exactly is your set up like (pics?)
Thanks!

fdracer

stupid question but on all cars what happens when you run out of gas and the engine cuts out? does the computer purposely cut out power or does the total lack of fuel just not allow the plugs to fire?

nocab72

I find it quite doubtful that your computer has any idea that you just ran the car out of gas, so it continues on it's merry way TRYING to ignite whatever happens to get injected into the chamber. If you are unlucky and are at WOT when you run out of gas, you'll likely go lean and detonate as air plus not-enough-fuel is injected by your fuel system, then bye-bye engine.

There does become a point where the air/fuel ratio is too lean and even though the plugs spark, combustion does not take place.

K

es

Here's the dented rotor:
https://www.rx7club.com/forum/attach...postid=1400006

This wasn't my motor, but belongs to forum member rx-007

& my 3-row.
https://www.rx7club.com/forum/attach...postid=1399962

Badog

I can attest to Nocab's expertise in tuning and addressing the temperature correction factors. Not that I need to.

Sounds like fuel. Running out of fuel under boost is death.

I am very sorry Z. Be glad to help when to works starts on it.

Tony

zayrx7

No, running out of fuel was not the reason my motor blew. The motor was already pop before that, I had plenty of fuel before that. I drove the car 20 miles up and 20 mile back on 1 rotor.

Terrh

iTrader: (7)

rotaries are amazingly hard on gas when blown, eh? I drove mine about 30km on a dead rotor and went through 1/4 tank...

1point3liter

That's my rotor. lol The rear rotor in my garage matches it. It actually has a worse dent.

I broke two apex seals on the front rotor, two corner seals (one on each rotor), dented both rotors, and chipped the front rotor housing at the top of the exhaust port. I might just get out the old die grinder and open up the exhaust ports some more to fix the problem. It looks like I might have a little excessive wear on the front side of the center housing. possibly from the broken corner seal? The motor was shut up imediately after the failure and trailored home.

When I pulled my turbo manifold I heard some rattling. I found my missing apex seal peices in there. Luckily the hurley's were soft enough that they didn't tear much up. I've got a couple tiny nicks in my turbine that I'm worried about. I'm tempted just to try it out since the are so small that and there aren't and clearance issues.

phatdex

Why would u be caning it when u have hardly any fuel? That just sounds silly.
Making sure u had fuel would be ur first priority, why would u wanna leave ur car stranded with no fuel?