Honda / Acura K20a K24a Engine Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
81 Posts
Discussion Starter #1
hello, i bought rdx injectors two months ago and installed them. After installation, i changed the injector size from kpro to 410cc and i checked the fuel tune on the road and everything is ok. After some days i noticed that when the engine is completely cold and completely hot engine starts perfectly but when i drive the car and stop around 1 hour, engine starts with just a little more cranking and after enginge start one or two second idles at 500 rpm and after idles perfect. I tried little more injector dead times, i tried -10% cranking fuel, i tried +10% cranking fuel but i couldn't find why. What you guys advise to me?

mods:
stock k20a with bolt ons
kpro
oem fuel rail
rdx injectors
walbro 255lph fuel pump
 

·
Registered
Joined
·
72 Posts
I'm just curious, why do you think it's a problem with the injectors? It almost sounds like what happens when not running an iacv in cold temps...
 

·
Premium Member
Joined
·
956 Posts
You just have to reduce cranking fuel trim. If 10% didnt do the trick, try 20, 30 and so forth until is perfect. Changing the injector size does not change the cranking fuel parameter. Cranking fuel trim does not affect the rest of your tune either, so don't hesitate to trim as necessary.


From Hondata:
Cranking fuel trim - applied when starting the engine. Note that the cranking fuel is automatically compensated for the injector size, but the overall fuel trim is not applied to the cranking fuel. Usually the cranking fuel can be left at zero
 

·
Registered
Joined
·
133 Posts
I had a similar issue when I had my hybrid racing fuel rail installed and RDX's.

Starting would be hit & miss, sometimes good starts, sometimes at least 4-6 cranks and when it does, it sounds like a subaru idling at 500rpm for 5 seconds, then back to normal idling.

Changed the fuel rail back to OEM with the fuel damper and its starting perfectly everytime.

Need to try and fit the fuel damper on the hybrid rail but need to source the male to male fittings.
 

·
Registered
Joined
·
1,594 Posts
One big problem with these RDX Injectors is that they do not come with any form of real data. Reusing the same dead times as the stock 310cc injectors is not correct and the actual dead times of RDX injectors are much different. They also flow slightly less than the "410cc @ 43.5psi" That they are advertised at. One more thing is they are not matched very well, A set that we have here that was flowed and tested showed a 6% difference in flow between the set of four, Most aftermarket injectors are matched within 1%.

In short its not surprising to see issues like this pop up, And honestly i'm surprised you don't see it happening more often.

IMO, The stock injectors are excellent and even respond well to higher pressures.
 

·
Registered
Joined
·
81 Posts
Discussion Starter #10
One big problem with these RDX Injectors is that they do not come with any form of real data. Reusing the same dead times as the stock 310cc injectors is not correct and the actual dead times of RDX injectors are much different. They also flow slightly less than the "410cc @ 43.5psi" That they are advertised at. One more thing is they are not matched very well, A set that we have here that was flowed and tested showed a 6% difference in flow between the set of four, Most aftermarket injectors are matched within 1%.

In short its not surprising to see issues like this pop up, And honestly i'm surprised you don't see it happening more often.

IMO, The stock injectors are excellent and even respond well to higher pressures.
Thank you for reply and information.
 

·
Registered
Joined
·
494 Posts
so is it a bad idea to use the rdx injectors since they are not matched closer? and by stock injectors do you mean the 310 cc?
 

·
Registered
Joined
·
45 Posts
Interesting, I've noticed that mine does take a little longer to start, but I never thought anything about it. I've had RDX injectors installed for about 1.5 yrs now. Gonna play with the Cranking fuel trim when I get home.
 

·
Premium Member
Joined
·
10,291 Posts
i have always had this issue with k series motors ive had, from aftermarket injectors to the stock 310's that come on the car.
 

·
Premium Member
Joined
·
5,000 Posts
These are the numbers that were used for a friends tuned k24a2 with RDX injectors.

Battery Voltage 7.99 10.01 12.04 14.06 16.08
Dead Time(ms) 2.55 1.80 1.41 1.10 1.04
I've seen those deadtimes before - I believe from some "WitchHunterPerformance" injector clinic or something. I have also read certain knowledgeable tuners state that they are not correct :coleman:

one of my buddy's has an oscilloscope which I might use on my set up
 
1 - 20 of 23 Posts
Top