Lean cold start EFI Setup

[jpilcher]

Hi All

I have been plagued with a lean cold start since converting to EFI. I am running a SDS EFI system which has a rich lean tuning knob.
I have checked the fuel pressure before start and it reads Zero psi. Once I prime the pumps it jumps to 43psi. I start the car, it seems to runs smooth for 15 seconds or so, then it leans out. If I turn the tuning knob to rich it smooths out again. Once the car is running for any length of time it is fine. If I restart the car it runs fine.
I am wondering if the rear pump check valve needs replacing. I have the feeling that the pumps are not fully priming the system.
If I leave the car sit over night fuel pressure drops to zero.
Another suspesion that I had was the size of the fuel crossover line, it is a 10 an line.
Too big? It was part of the GSF kit.

Any thoughts?

Thanks in advance.

John

[Tippy]

Sounds like your warmup curve is too short.

[philip j]

Originally Posted by Tippy

Sounds like your warmup curve is too short.

Sent you a pm john. Philip

[Tippy]

I never received it??

[lite75]

I agree with Tippy, check the length of your warmup curve.

[jpilcher]

Hi All

The SDS EFI utilizes a different strategy for warmup. It's combination of Start and Temperature fuel values. Phillip is going to give me a hand, he has gone through this on his setup. We are going to compare values.

Thanks for all your help.

J

[Speedfab]

What are you using as a temp sensor, the little Bosch 10mm threaded one in a cylinder head or the GM style CTS in your oil? Been some time since I've been in an SDS, but... When you start it cold, you can toggle between gauge 1 and gauge 2 mode, and see what knob percentage makes it run happily at what temperature, then simply go to the Engine Temp table and add that amount at that temperature breakpoint. The temp compensation table goes from no additional fuel at a value of 0 to an additional 100% fuel at a value of 255. So if you need to add 10% fuel at a given breakpoint, you need to add 25 to the number at that particular breakpoint. Once you get it sorted, you'll fund that the enrichment values taper down to zero in a pretty linear fashion. Make sure the values are zeroed above about 160 degrees F or so.

Comparing your table to someone else's will only really be useful if your injector flowrates are very similar. Because SDS uses raw pulsewidth in these calcs, the bigger the injectors the lower these values will be.

[jpilcher]

Thanks Speedfab, I will give that a try tonight.

[proffighter]

Here is my current (but still not perfect) mapping. What I can say, it's important to get a good temp value, made a clamp to fit sensor on the head fin. In your case you can also play with the high idle function until what temp it's in use. Further I set starting phase at 50 cycles for now. The column start values is only relevant during this phase, after that the normal temp values are used. Check the manual too, there is good info about setting. Finally I would not start tuning cold/start mapping before warm engine is done.

[jpilcher]

Thanks Roland

Your fuel table is almost identical to mine.
I ended up adding 7% across all the temp values, and this seems to have fixed the lean issue I was having. I checked engine temp
And tuning knob position where I normally start the car. I was able to determine that I was out by 7%. Car starts much better.
I just need to dial this in abit.

Thanks for everyone's help.

Regards

John

[Speedfab]

Excellent. I had an SDS in my 911 a loooong time ago. I think I was Ross's Porsche guinea pig in fact. Hard to believe it was 17-18 years ago.

I just looked and it's still on their customer page from 2000:

My car back when 500whp was "a lot"

[Tippy]

Originally Posted by Speedfab

Excellent. I had an SDS in my 911 a loooong time ago. I think I was Ross's Porsche guinea pig in fact. Hard to believe it was 17-18 years ago.

I just looked and it's still on their customer page from 2000:

My car back when 500whp was "a lot"

Very sweet ride! That's some big hp for a 3L.

[Speedfab]

Originally Posted by Tippy

Very sweet ride! That's some big hp for a 3L.

Tell a Supra guy 500 wheel is a lot for a 3 liter, lol.

Thank you, that car has been my "baby" forever, I still have it. That engine was 3.2L and it ultimately made just shy of 700whp with a single, but the binary power curve left a lot to be desired. It is much different and far more powerful now - there were a lot of compromises back in the late 90s that no longer exist today. Sometime soon I will start a thread... I belonged to this forum (or a previous version) a good while back, but I can't remember my info.

I built these around 2003 just after I swapped in a 6 speed G50, and things just continued to escalate from there:



I just recently finally found time to put it all back together, and I started back looking at this forum for motivation. Thanks again for the kind words.

Tracy

[Tippy]

Yeah, you're going to have to start a thread....

Love to see some specs!

[Rawknees'Turbo]

Originally Posted by Speedfab

I belonged to this forum (or a previous version) a good while back, but I can't remember my info.

You're not the only person here who's had to create a new user ID, butt the reasons for needing to do so vary!!!


PS - looking forward to reading, and learning from, your expertise!

[Speedfab]

Originally Posted by Rawknees'Turbo

looking forward to reading, and learning from, your stupid mistakes!

Fixed.

[Tippy]

Originally Posted by Speedfab

Fixed.

We're still waiting for that thread!!!

[Rawknees'Turbo]

Originally Posted by Speedfab

Fixed.

Ha ha - yep, butt no harm in mistakes - takes big "you know wutz" to head down that road in the first place!

[Speedfab]

Originally Posted by Tippy

We're still waiting for that thread!!!

Patience Grasshoppa. Isn't Juan Ruiz still around? Look at his car and imagine it silver for the time being.

[Tippy]

Originally Posted by Speedfab

Patience Grasshoppa. Isn't Juan Ruiz still around? Look at his car and imagine it silver for the time being.

Ok, now I'm calling BS....

Juan has an absolute monster.