Mon projet, Mazda RX7 1989 LT1

Purple Poncho said:

It is great to see guys still supporting the old LT1.

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Do you still have the TA? I remember one day at Napi, you were trying to get into the 10's... you had done a couple 11.0x passes that day.

Yes, I still have it.

I remember that day. I eventually got it to go 10.6 with a best mph of 137. The combo has changed a bit since then but have been working on some gremlins the past few summers.

Purple Poncho said:

Yes, I still have it.

I remember that day. I eventually got it to go 10.6 with a best mph of 137. The combo has changed a bit since then but have been working on some gremlins the past few summers.

Click to expand...

Have you done anything to it since then? Will you race it this summer?

It would be fun to see it at the track.

I blew that motor 4 years ago. It was a 383 with stock heads and is now a 355 with the Trick Flow 21* heads.

I have not raced it since I killed the motor and it is not 100% to my satisfaction since I got it back from the shop 3-4 years ago.

Sweet. Mine is also a stock stroke motor with ported TFS heads.

What are the bugs that need taken care of?

What head unit are you running, D1SC?

I have been chasing this problem for a few summers and I can't beat it.

The problem: 1/ plugs are rich/black
2/ 02s don't move from high 800-low 900s at idle, over 8%TPS the move normally
3/ Number 5 header tube reads at a higher temp with the IR gun
4/ I have tuned it all kinds and don't think it is the tune
5/ I've changed plugs a bunch of times, changed the plug wire on #5 and swapped the injector from #5 to #2 and none of this changed anything

If I didn't know any better (I log with TTS every time I drive and check plugs) I would say it was fine. It idles fine but seems to want to run on the rich side according to the 02s at TPS% of 8% and below.

I think the #5 cylinder is rich for some reason and causing fuel to be dumped at low to no load. Not sure what to do at this point. Could be an intake leak or vacuum leak but I've checked and don't hear or see anything. BLMs are not lean.....Stumped.

It has a maxed out Vortech T trim on it.

What plugs are you running? Have you tried playing with the individual cylinder fuel trims?


Reçu ça pour le RX7:

Nice. That should make it easier.

I mainly use NGK BKR6E and once used Autolite AR3923. I am hesitant to use the fuel trims at this point because I am convinced it is a mechanical problem and don't want to make a problem cylinder worse. It is kind of a dichotomy. The 02s and plugs say rich, high temp on cylinder says lean. I think there is something making that cylinder lean casing the pcm to dump fuel...but only under very light throttle and idle...but that is just a theory. Anything above 8%TPS is great.
I don't think it is possible but I wonder if the opti could make only one cylinder have weak spark. I've chekcked the fuel regulator, vacuum leaks, header leaks...but I do have miles of vacuum line and will go over it carefully this summer.

"high temp on cylinder says lean"

You mean high temp on the header tube? Because a rich cylinder will raise header temps.

What does you closed throttle timing table look like?

Yes high temp on the header with an infra-red gun. I originaly thoght rich with extra fuel being dumped but the internets says high temp is lean.
Idle timing started at 22.5 and is now 26 as commanded in LT1edit and bounces 25-29 as logged with TTS.
I wonder if the rocker needs adjusting. I don't hear anything wrong but it is loud with the blower etc.

At idle, rich or not enough timing will heat up the exhaust pipe.

25-29* is enough timing at idle IMO.

Did you take a compression test on that bank? Could low compression make for a lazy cylinder and heat up the exhaust pipe?

No I have not done that and now you are starting to touch on my fears. LOL

I'd check compression just to rule it out.

Then check out the individual cylinder fuel trims, there's one for idle and one off idle. See what value you have for #5 and change it to see if it helps.
If it helps, then you know it's fuel related.

Did you try the quickstart spray test for vacuum leaks?

I would hope it is not a low compression cylinder. It is a fairly fresh motor with 4 years of 2000km/summer cruising and under 10 hard pulls. Plus #5 is a bitch to get at with my headers.

Quickstart spray method?? I am guessing spray quickstart around the intake and see if the RPMs drop or rise?
Sorry to hijack your awesome thread on your cars btw.

Spray around the intake and see if the RPM rise.

I'm thinking it might be a tune issue, maybe just a weird number in the individual cylinder trims @ idle.

Thanks for the tip. I'm pretty good at tuning and have had it so lean it will lean pop and even stall from lack of fuel. The trims are stock and the same as the last combo. There is a problem somewhere and I think it is not related to fuel or spark. I was going to replace the fuel pressure regulator and get e injectors cleaned just in case.

I did simulate a vacuum leak and didn't get the lean ( green blm) that i did on the last combo so maybe it is a small leak somewhere. when the throttle blades are closed or near closed and not much air is getting in, it affects the 02 readings more and when it is above 8% tps more air, more velocity over comes the small leak and the PCM is happier.

update!?

oui, mais rien de super intéressant pour vous autres...

Les brakes sont faits, j'ai enlevé l'ABS et refait les lignes en acier. J'ai changé le booster et le master pour un set qui vient d'un 929, c'est plus gros et devrait améliorer la performance au freinage.

J'ai aussi fait de la place dans le devant du char, j'ai enlevé le genre de tube qui tenait le rad et plein d'autres brackets et gugusses inutiles. Présentement il n'y a rien en arrière du bumper, tout est enlevé. Va falloir que je figure comment je vais placer le rad et l'intercooler pour que ça soit le plus compact possible, pas le choix avec un T6 faut trouver de la place.

J'ai fait le premier test-fit du moteur dans le char, ça accote partout...
Les valves covers accotent dans le firewall et le hood ferme pas à cause du throttle body. J'ai fait des notch dans les valve covers, reste à modifier le coude pour baisser le TB et on se croise les doigts pour que le hood ferme. Y'a aussi une des hoses du heater core qui arrive direct dans le valve cover. Je vais voir comment je peux y remédier, probablement rediriger la hose de l'intérieur du char et la faire sortir par un des trous ou y'avait les hoses de l'AC que j'ai enlevé. On verra.

Sur la suspension arrière j'avais aussi un trouble de clairance entre le bas du shock et le tube du diff, j'ai du faire usiner des notch dans les shocks pour éviter que ça frotte. Il y a aussi le centre du différentiel qui est presque accoté dans un cross-member dans le plancher de la valise... J'ai environ 1.5" de clairance entre le diff et le cross-member. Ça ressemble a un beam de 4"x4" dans le plancher, va falloir tout défaire la suspension arrière pour aller couper une notch et enforcir cet endroit si je veux pas être obligé de "jacker" le cul du char pour que ça claire.

Bref, le char est minuscule et y'a rien qui fit. Pour ceux qui ont jamais vraiment pris le temps de regarder un FC et le comparer a d'autres chars, dites-vous que c'est à peine plus gros qu'un Miata. À coté d'une Mustang ou une Camaro le RX7 est vraiment petit...

Une coupe de photos du moteur avec les valve covers revenus du powdercoating. Je vais avoir plus d'updates bientot.



Close-up pour montrer la texture dans le powdercoat


J'aime ca monochrome...

Beautiful. Your car is so clean you could actually get sponsored by