Injector size and ECU map

[Rob_DSM]

So as I understand it, the computer will give you a gradual advance in timing as your rpms go up, assuming things are in good tune. I also understand that at higher airflow levels, the computer will not give as much timing advance.

When you get bigger injectors and modify the airflow signal to trick the computer into thinking less air is flowing, you get more timing than you would have before.

My question is at what point do larger and larger injectors with their accompanying "less" airflow cause too much timing advance and therefore knock? I'm trying to decide whether I want 550s or 660s or something. I know 550s would be fine for a 16g, but like I say, would the timing advance be too much with the 660s? Thanks.

Robert

 

[Rob_DSM]

I'm about to get some 660s. I'm expecting a 16g in the mail soon. Is this too injector much for that turbo? I do plan on upgrading the turbo to something larger when I have my full suporting mods. Thanks.

 

[Bohrn]

to both of you:

It all depends on your current mods, your future mods and what your expectations are.

I'd say the bigger ones would do you fine as long as the rest of the engine is not stock.

Oh and just incase(no insult intended)no one mentioned it to you, the stock pump will not be able to send enough fuel to either set of injectors. It can't handle the stockers.

 

[laza101]

Well, I just put 510cc injectors in my 16g-equipped car and at 17psi I'm still running about 90-95% duty cycle (down from 105%). My timing has not substantially increased - time for more fuel pressure, and if that doesn't work, 550's. 660's, on the other hand would be overkill in my opinion - unless your car has many other mods.

 

[kpt4321]

510's are not even worth the money. In my opinion, 550's are still a bit too small for most people. I have seen 550's close to 100% on cars with 14b's and pump gas.

You won't have to worry about "too much" injector with 660's....you can always just richen it up a little, or retard the CAS, in order to get timing where you want it.


....Kyle T.

 

[Bohrn]

Kyle, explain this retarding of the CAS for us illiterates

that is where we set the base timing with the grounded plug on the firewall right? It is the round thing on the passenger side of the valve cover correct??

Now why do we want to frig with that to correct for fuel??

 

[FastRthenU]

Im running 870cc injectors with a S-AFR and IM having no problem with timming advance. I even have my bad timing raise to 8 degree's instead of 5. my mods are in my list

 

[MNGSX]

Big injectors = when you have an ample engine management system to fix the idle.

http://www.roadraceengineering.com/1gcasin2g.htm

Set the base timing:

1. Connect a timing light to battery power (+ and -) and the Number 1 spark plug.

2. Connect a data logger to the car and display timing advance and RPM

3. Allow the car to come up to temp. Coolant 212 deg F, 750 RPM +/- 100, Fan's should cycle on and off

4. Read the timing from the crank with no load on the motor. Each mark is 5 deg no fans, no lights, no A/C etc.

5. Adjust the position of the CAS until the readings from the TIMING LIGHT, match the timing advance displayed on the data logger. This is "stock" advance. If you have a mild setup with stock cam's you'll pass the smog inspection if your ECU timing and crank timing reads 5 deg +/-3 deg BTDC at idle

6. Add additional timing at own risk, (Timing light advance) - (ECU advance) = (Base Timing Shift) see: "The bad"

7. Tighten the 12mm nuts/bolts that hold the 1G CAS

 

[Rob_DSM]

Originally posted by kpt4321
510's are not even worth the money. In my opinion, 550's are still a bit too small for most people. I have seen 550's close to 100% on cars with 14b's and pump gas.

You won't have to worry about "too much" injector with 660's....you can always just richen it up a little, or retard the CAS, in order to get timing where you want it.


....Kyle T.

I can't do that with a 2g can I? Sorry, I'm still a little new to all of this. FWIW I already got the 660s now, so I hope I can make them work well with the AFC.