Too cold to start
 

Hi Gang,
Here's my setup on '88 TII

Atkins street port
550/750 RC Engineering injectors
Racing Beat Turbo Back exhaust
Microtech LTX12

So the recent cold snap did not sit well with my car and I've been hours late to work twice. This morning it was -18C (-1F) and it cranked fine but no ignition. I had a in-hose water heater plugged in all night as well as trickle charger on the battery

Tonight the forecast is -26C, so I expect trouble in the a.m. Any suggestions on what (and how) to tweak on the LTX to get ignition at sub-zero temps?

Thanks!

- kel -

Check your maps that relate to temp i think there are 4 from memory.
Quite often a tuner wont input any values in the lower temps if they think the car will never operate in those conditions.
If you do have values for those temps try upping the mixtrim whilst you are cranking.

Thanks!


I'll give the mixtrim a try. You're saying that the lower temps should be richer?

The colder it is the more fuel is required to start. These temp points are usually guesstimated by the tuner and may be out.
If the car was tuned in a warmer region you may have no values at low temps.
Do you have a handset?

I had this very issue , my car would hate the cold to start . need to add a bit more fuel

Okay! The Rx7 Club does it again!

Couldn't find my handset, so put the laptop on it. Right now, it's around -19C (7F) and the car won't start. The original tune was done in Montana, so you'd think the cold stuff would've been covered. I had it tweaked here in Colorado by Mac Autosport (a great shop by the way) but it was summer and cold never entered the conversation.

ANYway...I have the in-hose heater plugged in (drawing 600W) and in the water screen of the software, the 18 degree block is highlighted so I can conclude the heater works. But that doesn't help the starting.

Next, I flipped over to the air screen and found that in Air_t the highlighted block - and ones on each side - were zeros. I selected the highlighted one and while cranking I started dialing it up. Lo-and-behold. It lives! I added some to each side block to make a smooth curve upward as temp goes down.

And, now that I know the what-and-how, I'm confident I'll make it to work on time Monday (forecast overnight -20C)

Thanks,000,000 (that's thanks-a-million) to you guys and chalk up another win for the best forum on the net!

- kel -

.

Good to hear its going:)
Sounds like it was too rich at that temp.
I personally would have changed the crank map down. in my limited experience you have done the" two wrongs make a right" to get it to start as the car will run leaner in all maps at those air temps with the correction you have made.
So you have made a rich crank start with a lean air temp.

I thought about the Crank map too, but it already had a pretty steep curve up as temp goes down. I didn't do Water, because the in-hose heater was doing its job and water temp was about 30C above ambient.

Air_t had zeros from about freezing down and bumpin it up about 10% at ambient seems to have done the trick. I'm going to test it again in the morning, as we're having another way sub-zero night forecast.

I'll update with specifics.

- kel-

.

Honestly how can people put advise on this forum when they have no clue?

Too rich at the temp?Really?
He added fuel and it started.....

As for adjusting the air temp correction your adjusting the wrong maps.

If it runs fine at that temp once started then you need to be adjusting the crank map. If it stalls at that temperature once on you need to be adjusting the water map.

What ever you dailed into the air temp map take it out and put it on either crank or water depending on what fits as per above.

Thanks for pointing that out rx72c :( Op had an urgent prob and no help so i thought id help best i could.
Kel follow what rx72c says as he knows exactly what hes talking about.

What are these maps, and how to hook up a laptop to the car.
I have an rx7,stock motor,and it is not starting in the morning.
I have the manual,and going through it now.

You need a laptop with a serial port, the Microtech dongle, and the Microtech software.

The manual is downloadable from the Microtech website and describes the temperature compensation functions.

If you honestly have zero experience, it's best to get the guidance of someone who has done this before.

Thanks. I have no experience and the start assist has been removed already.