SR20DET tuning questions.

[Josh K.]

I finally got around to hooking up my MAP-ECU and started tuning yesterday.

www.mapecu.co.nz

I have a..
1989 240sx
S13 Blacktop SR20DET
FP-Big28 turbo
Hybrid FMIC
Walboro pump
Megan manifold and turbo outlet
Apexi N1
everything else stock including injectors

Once I have a solid base map I plan on posting it for others to start with.

So far it runs pretty strong, up to 5psi accerating its 11.5-12. idle 14.7, decel 20.

My questions so far is:

1. what afr should I look for at say 2500rpm, 5th gear almost no load, just barely any throttle?

2. what afr after chopping the throttle from a high load run to 7K?

3. why would my car be 18.7 when cold at idle but 14.7 when warm? temp sensor?

4. if I go from 370cc to 550cc injectors will I have to redo the whole map from scratch?

Thanks Guys

Josh

[Josh K.]

no tuners here?

[smelly240]

ive never used that piggyback before... i run a maf still. i was told by some supra guys u can "scale" for injectors.

[Josh K.]

this is just general sr tuning here, no one knows the answers?

[GSXRJJordan]

I'd shoot an email or PM over to Steve Shadows, he's a local tuner here in socal that probably knows all that off the top of his head. For a cruising/low load AFR, 14 is fine. Uppin the injectors requires redoin the map, but it's all taken down by a certain percentage, so it's not as bad as it seems. I was going to use the MapECU2 on my SR, might have to hit you up for your map when you've got it all worked out

[Josh K.]

Thanks.

I'll be sending my map to map-ecu once its all dialed, then again once I get the new injectors in. I plan to go with the MAP-ECU2 in the future also to get the launch control.

So far I'm pretty solid all the way to 12psi. I'm very pleased with the ease of tuning and now having no MAF in my car.

My only real issue is cold start lean running. I have yet to figure out how the sr regulates fuel when cold. I would assume it looks at the temp sensor then richens the map, I'm gonna check my sensor and see if its bad. I'm leaning to 18AFR at idle until warm then it drops to 13.7

[Josh K.]

temp sensor shows 2.6k when cold, which is perfect, hmmm.

[GSXRJJordan]

yeah that's a bit backwards... should run a bit rich at startup. Even so, 18 isn't the end of the world, just don't drive the car until it warms up. Have you thought of just ditching the temp sensor completely, so it reads "warm" all the time?

[ae86diego]

do you have any type of idle air control valve?

[GSXRJJordan]

Of course, the IACV is still controlled by the stock ECU (MAP-ECU is a piggyback), so the IACV is still working the same as usual. Any manual changes to the IACV wouldn't change the idle problem because that air is still metered.

[Josh K.]

I'm still struggling with the cold idle. But....

I have to say the guy at MAP-ECU is topnotch, he made a special firmware and converted table for -25inHg to +27.5psi with 2.5psi steps for me. the sr dips to -25inHg when the scale was only -20inHg. now thats fixed with the new firmware. turn around time from me emailing him to a new file was 30min!!!! he even reworked my map to fit the new scale.

I'll post up a full review with dyno sheets and all my files when I'm finished. Once I'm dialed I'll be upgrading to the MAP-ECU2!

[RACETUNE]

1. what afr should I look for at say 2500rpm, 5th gear almost no load, just barely any throttle?
*the a/f will be lean

2. what afr after chopping the throttle from a high load run to 7K?
*you need to trim the a/f, depending on your load and are you over running the injectors?

3. why would my car be 18.7 when cold at idle but 14.7 when warm? temp sensor?
*the map ecu, can not change that parameter. all it does is it generates a signal to the ecu so you will not need the MAF anymore.

4. if I go from 370cc to 550cc injectors will I have to redo the whole map from scratch?
*you should always tune the car from scratch, usually the base map they offer are only to get the car started and you play with the software from there.

Racetune

[johngriff]

Your idle map should look close to the same between the injectors. But keep in mind this device is the same as a apex-i SAFC II, just with a laptop interface and map conversion.

The amount of boost you are putting down right now is so so for that af/r, but i would look into 11.3-11.5 at the leanest for pump gas.

The biggest question to ask, is how altering the maf signal to force your injectors to act as you choose, will affect the ignition timing. Since the timing is calculated the same as the injector time via the MAF signal, you could be looking at some pretty horrible timing issues.

That is my guess, why they released a v2 with timing control. Not to "utilize the most aggresive timing possible", but to correct for bad timing numbers.

Does the unit you have provide injector duty cycle, or MS open time. How are you programming the fuel table? Desired af/r, ms open time, lambda/1?

[Josh K.]

I have an Innovative wideband and log data vai the MAP-CAL software. I don't know injector duty just voltage from the MAP-ECU.

The fuel table is programmable through the MAP-CAL software

So what your saying is get the afr down into the low 11's and get some sort of timing control or upgrade to MAP-CAL2?

[johngriff]

can you take a screen shot of your fuel tunning table and host it? if you have trouble hosting, you can email it to me, [email protected]. Fuel injectors do not work off of voltage, they are a oscillating device (on/off). The ms open time represents the time "on" the fuel injector is during the stroke. This would let me know if you are maxing out your injectors, though, as with any maf interference device, you can only send the maximum value allowable at the end of the factory ecu's fuel table.

Yes, start pushing the af/r's down into the low 11's if possible, and get some kind of timing feedback at least (apexi multi checker... i think apex has another box out that will feedback timing), preferably something that can datalog the timing, though i cannot recall a box that will do this. Because the map-ecu is making changes to the maf signal, it is changing the timing when you change the "fuel/load" value.

[Josh K.]

Keep in mind most of the 12psi and up range haven't been tuned, I know its maxed now thats why I'm getting bigger injectors. right now I'm sitting at around 11psi max.

4095=5v

[johngriff]

yikes, tunning via voltage.

I dont know if i can recomend this, the accuracy cannot be very very good, since the voltage value is a request to the ecu for injector duty, not a dictation.

Yes, you will need larger injectors. You will also need to get a handle on your timing. Remember, that the volume of gasoline in the combustion process only dictates the cylinder temperature, and that the ignition timing itself is what is going to produce hp and tourqe.

As for your cold start map, there is not much you can do, as stated above. Taking the car to the dyno to get a look at the timing values would be good. I see you are in Hawaii? I heard the only dyno shop there recently closed down, as well, they took out your race track.

[Josh K.]

I'm in Maui, we have a shop with a dyno. 1320 pefromance.

So are your saying if I want to have a real good tune my choice is Reflashed ECU+Z32 MAF or Haltech type standalone?

[johngriff]

Those would be some good options, whatever you get, you are going to want to make sure you have the most accurate access to the tuning tables of the ecu as possible. If you go the reflashed ecu, does 1320 tune EPROM? It would be best to get the tune done there, on your vehicle.

[Josh K.]

No, I was thinking like Enthalpy or someone that knows sr's. 1320 does mostly honda's.

I was hoping I could use the MAP-ECU so I didn't have to spend tons of money to get 325whp.

[johngriff]

most 2871r setups do not seem to exceed that number without ignition tunning. An enthalpy ROM tune might be the way to go.

[Josh K.]

I think I'll piggy back the MAP-ECU with a bikirom.