Morebst7

iTrader: (8)

This is my first post on here so if anyone could point me in the right direction for reposting in the correct thread it would be appreciated. Lets get to the issues:

Recently bought my FD and so the project begins. I had a hot start issue that the previous owner believed was an issue with the stock coils not producing enough spark. On a cold start it would turn over on the first crank and after cooling for 20-30 minutes would start fine. The car sat for a week while i was out of town and on the first two cranks wouldn't turn over. I didn't want to flood it but we popped the hood and it was pretty rich so we pulled the relay and cranked it, replaced it, and still nothing. While cranking the exhaust is kicking smoke which leads me to believe it is getting fuel just fine. I've push started 3 times since this issue and it starts right up and idles around 1800rpms as usual and Fuel/Air is around 11.5-12.

While driving with gradual acceleration it still has strong pull, however if I put the pedal down before 4k-4.5krpms with approx. 8psi boost I get strong sputter. After the boost is built up to roughly 8psi and I'm above 5krpms acceleration is strong with no issue. This was never an issue before and seems to be connected to the starting issue as it never happened prior.

I understand that it is either fuel, air, or spark causing the issue and that there is a lot built on this making it hard to troubleshoot. I'm new to the car and new to the build aspect of rotary engines so anything is helpful here. Thanks in advance for any advice!


Mods:
Aggressive street port
3mm Cryo treated Apex seals
Rebuilt block (11k miles)
OMP delete (runs premix)
Pineapple Racing water pump pulley
Aluminum pulley set
FC Thermo switch
Garrett TO4R Single Turbo
PWR core custom intercooler
HKS GTII 60mm wastegate
Tial Q BOV
Apexi Power FC with commander

Fuel:
850cc primary injectors, 1600cc secondary
KG parts fuel rails
Nippon Denso Fuel Pump
Aeromotive FPR
FJO Peak and Hold injector driver

Sgtblue

iTrader: (16)

I'm not a tuner, nor experienced with single turbos. But what your describing...poor hot starting, is usually associated with low compression. Before doing a lot more I would recommend checking that. While there are specialized tools for checking compression on a rotary, there are simple and inexpensive ways to get an idea of where you stand...
Rotary Resurrection home of the budget rebuild.

Morebst7

iTrader: (8)

Thanks for the quick reply. I can give it a shot tomorrow checking the compression but as far as I know the treated seals and fresh rebuild shouldn't be causing the issue. Correct me if I am wrong but wouldn't a compression issue have a sputtering/bogged performance damper all the time while driving as well as a rough idle?[IMG][/IMG]
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Sgtblue

iTrader: (16)

I'm not a builder, maybe one will chime in. This will bump it back up.
But not necessarily. It's precisely the fact that you have internal modifications like an "aggressive" port and 3mm seals (along with poor hot-start) that give rise to my suggestion of low compression. Who did the porting and how well was it done? Who did the machining on the rotors for those over-sized seals. And IIRC 3mm seals tend not to seal as well anyway. And what shape were the housings in?
Just because it was recently rebuilt doesn't guarantee good compression either. Were new seals springs used? What shape were the housings? Were new side seals used? If so, how were they clearanced.

And no offense meant, but I see some questionable things under the hood from the previous owner. Things a reputable shop would not have done, which suggests that it may not have been a reputable shop that did the rebuild.

Morebst7

iTrader: (8)

The work for the rebuild was done by a Mazda master mechanic. He has worked on the 13b for years and rebuilt several of them. I'm going to look into the compression but I also want to check the plugs. I'm stuck working in a parking lot right now I don't have access to a shop which causes the issue of getting to them. I'm lowered 2" so going from the bottom which looks like the easiest way is out of the question. Do you have any experience with pulling them? I don't want to get knee deep into ripping things off to find that I'm not equipped with everything I need to access them

Sgtblue

iTrader: (16)

IMO, changing plugs from below is preferred. But actually the FSM suggests they be done from above. ---> https://www.rx7club.com/3rd-generati...wnload-449950/
*Remove the compression tube (in your case, the Greddy Elbow). Take care not to loose the big 'O' ring. That should give you access to the plugs. (FSM pg G-18) Coils are another issue. (FSM pg G-20)
*Be sure to use a plug socket, thin walled is easiest.
*Do one plug at a time. The plug wires are easy to cross up.
*Use a bit of low-temp anti-seize on the plug threads before re-installing.

Morebst7

iTrader: (8)

Thanks I'm going to give it a look and go from there

Morebst7

iTrader: (8)

Update: Checked the plugs and found that one of the trailing plugs were completely cracked on the ceramic end. Aside from that they were not too worn. It still fails to start with the ignition, but we push started and the sputtering is gone.

The next question is whether this is an issue with the tune or if the ignition coils need to be upgraded. I've searched on the AEM smart coils and looks like that may be the upgrade to solve the issue. Any suggestions on whether to try a tune first or upgrade and tune after?

Slowtary

You can always test the coils, there is no sense in replacing good working parts, do you have anything that tells you who tuned it, if you do call them and see if you can talk to the guy see what he did (Some weird ways they did things to that engine bay) If you don't I would take it to a tuner you trust or has good history with these cars (Good luck depending on where you live)

trinirx

any updates on the hot start issue?