black93RX7

I have a 93 FD with a LT-8, T78, stret port, 850cc prim, 1600cc sec, supra fuel pump, stock coils, HKS twin pwr

I adjusted the timing last weekend and after the car felt hesitant and had what I think is bad ignition breakup above 3500rpm. The car will rev up but sounds like its has serious detonation or ignition break up.

The timing was put back to its previous setting and the problem still persists. The car runs fine at lowers rpms and highway cruising but uses an excessive amount of fuel and gives off large clouds of blue smoke when shifting gears at higher rpms.

he car only runs off leading plugs (trailings are capped) and is pre-mixed so fuel milage has never been great and a bit of smoke is expected. However, now I only get aprox. 200 km out of a full tank of fuel and there is a large cloud of blue smoke when shiting gears.

I am not sure if there is a problem with the ecu, coils, tps.

The timing was changed to:

T_RPM

500rpm = 8
1000rpm = 10
1k - 3k = 10-28
3k - 8k = 28

T-MAP

30 - 0HG = 0
oHG - 4psi = -5
4psi - 8psi = curve to -10
8psi - 14psi = curve to -14
14psi - 20psi = cirve to -20

Origional timing values:

T-RPM

500 - 1k = 25
1.5k = 20
2k = 17
2.5 - 4k = 15
4.5 - 6.5k = 16
7 - 9k = 13

T_MAP

30HG - 15HG = +8
10HG = +2
5HG - 2psi = +00
4psi = -01
6 - 14psi = -03
16psi = -09

After the problem occurred the timing values were changed back to their origional values and the problem persisted. I changed the spark plugs and it had no impact. Fuel pressure is fine at 30psi base, oil pressure is also fine. I always use 94 octane fuel premixed with 4oz of two stroke oil.

Also, have large flames from exhaust on decel. The car war running fine proir to the timing adjustment.

Anyone have any suggestions?

Thanks

10sec rx7

are you sure you have the right triggers hooked up to the leading coils??

black93RX7

yeah, I didn't change anything else except the timing. I am going to try and switch in a leading coil from an FC to see if it makes a difference.

black93RX7

I swapped in a fc leading coil and the car still has severe misfire at high rpm's and is blowing alot of smoke.


Now I am thinking it could be a secondary injector problem or a broken side seal, corner deal or apex seal.

Any ideas?

bob13bt

iTrader: (9)

A compression check should rule out internal engine problems.

How is the fuel pump? Or the wiring to it?

black93RX7

The engine compression has always been at 60psi since it was rebuilt last summer, it now has approx. 6000km's on it.

Today I did another compression test and it still showed 60psi, however when both leading plugs were taken out and the motor turned over the front rotor sounded uneven.

I talked to the builder and he says it sounds like a bad corner or side seal. He doesn't think its an apex seal since the car still idles fines and revs up.

the fuel pump seeems fine and the fuel pressure is normal.

If I can't find anything else that may cause this type of problem the motor will be pulled, probably in the next few days.

MARTIN

Yea, if the comp is still 60, then you need to go back to builder.

black93RX7

The fun job of pulling the motor has started. Should have it stripped down to the block tonight and hopefully open it up by tommorow.

I am going to video tape and take pictures of the disassembly of the motor just to cover my ***. Can;t wait to see what I find.

black93RX7

The problem turned out to be 5 broken corner seals and a broken side seal. It turns out my low compression may have been due to wear on the end plates. I was under tghe impression the builder had lapped them but it sure doesn't look like it.

MARTIN

That sucks, and you should also mention that it never went past 60. That should either get you a rebuilt motor for free, or atleast not have to pay for any labor

Aaron Cake

iTrader: (1)

Let me guess, RX-7 Specialties built the engine?

andre sinclair

iTrader: (36)

I hope for your sake you have another builder!

How can one forget to lap the plates on a freshly rebuilt motor?

puntorotary

Ive never had the plates lapped,and ive built several engines,and ive never had that problem before,theyve all ran nice and hard and lasted a good while.Whoever built your engine just either didnt know what they were doing or just were in a hurry and didnt care to put the right amount of attention "and love" to the engine rebuild.

rx72c

iTrader: (8)

Who says you need to lap your plates?
Ive built plenty of motors without lapping plates. As long as they arnt excessively worn they are fine.