D17A7 CNG engine converted to Petrol knocking issue
03-08-2017
#1
Registered!!
Thread Starter
Join Date: Mar 2017
Age: 43
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 
D17A7 CNG engine converted to Petrol knocking issue
I am total noob when it comes to engines and performance.
I have swapped my D15Y3 with D17A7 non vtec in Civic 2005. As you might know better that D17A7 is from Civic GX which is a CNG engine with 12.5:1 compression. We converted it to petrol, used injector rail, throttle body, transmission, ecu and headers of old engine D15Y3. We don't have O2 sensors in this model in our country, moreover ECU don't have knock sensor option.
Engine is in great shape and giving overall excellent performance, the only issue which I am facing is knocking. I am using 95 Octane, but still its knocking during quick acceleration. My mechanic is suggesting to retard the timing to fix knocking.
Experts, please suggest what are my options to fix the knocking problem and how we can get maximum power out of this engine.
I have swapped my D15Y3 with D17A7 non vtec in Civic 2005. As you might know better that D17A7 is from Civic GX which is a CNG engine with 12.5:1 compression. We converted it to petrol, used injector rail, throttle body, transmission, ecu and headers of old engine D15Y3. We don't have O2 sensors in this model in our country, moreover ECU don't have knock sensor option.
Engine is in great shape and giving overall excellent performance, the only issue which I am facing is knocking. I am using 95 Octane, but still its knocking during quick acceleration. My mechanic is suggesting to retard the timing to fix knocking.
Experts, please suggest what are my options to fix the knocking problem and how we can get maximum power out of this engine.
03-08-2017
#2
If you think a good mechanic is expensive, try hiring a bad one
Re: D17A7 CNG engine converted to Petrol knocking issue
Lean rattle? Fuel delivery may be a big problem (lean in open loop and max load).....Bigger engine needs more fuel then the smaller engine did.....so...
FIRST I might install a set of injectors from a D17A2 before messing with anything else.
Other thoughts:
Octane booster?
You could back off the timing, but you may give up quite a bit of power.
Between the various versions of the D17 engines (A1, A2, A7): Figure out if the combustion chamber size is different or if the pistons are different, in order to lower the static compression ratio. Would you have to swap the head, or swap the pistons, or maybe both, in order to get the compression ratio into a more acceptable range.
FIRST I might install a set of injectors from a D17A2 before messing with anything else.
Other thoughts:
Octane booster?
You could back off the timing, but you may give up quite a bit of power.
Between the various versions of the D17 engines (A1, A2, A7): Figure out if the combustion chamber size is different or if the pistons are different, in order to lower the static compression ratio. Would you have to swap the head, or swap the pistons, or maybe both, in order to get the compression ratio into a more acceptable range.
03-08-2017
#3
Registered!!
Thread Starter
Join Date: Mar 2017
Age: 43
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: D17A7 CNG engine converted to Petrol knocking issue
Lean rattle? Fuel delivery may be a big problem (lean in open loop and max load).....Bigger engine needs more fuel then the smaller engine did.....so...
FIRST I might install a set of injectors from a D17A2 before messing with anything else.
Other thoughts:
Octane booster?
You could back off the timing, but you may give up quite a bit of power.
Between the various versions of the D17 engines (A1, A2, A7): Figure out if the combustion chamber size is different or if the pistons are different, in order to lower the static compression ratio. Would you have to swap the head, or swap the pistons, or maybe both, in order to get the compression ratio into a more acceptable range.
FIRST I might install a set of injectors from a D17A2 before messing with anything else.
Other thoughts:
Octane booster?
You could back off the timing, but you may give up quite a bit of power.
Between the various versions of the D17 engines (A1, A2, A7): Figure out if the combustion chamber size is different or if the pistons are different, in order to lower the static compression ratio. Would you have to swap the head, or swap the pistons, or maybe both, in order to get the compression ratio into a more acceptable range.
03-08-2017
#4
If you think a good mechanic is expensive, try hiring a bad one
Re: D17A7 CNG engine converted to Petrol knocking issue
Pistons of D17A7 are different.
I know the pistons are different between the 3 common versions of the D17 available in the USA, though I am not familiar with the versions of this engine available in your area.
https://en.wikipedia.org/wiki/Honda_D_engine
I think injector size of D17A2 is 240, can you please confirm.
You'd have to research this yourself.
More ideas:
Trying to think of ways to take advantage of the high compression, instead of trying to de-tune and limp around with a less-than-ideal swap choice.
Alcohol injection on demand? Methanol injection? Alky+H2O injection?
Just as an extra fuel enrichment and cooling kick for those high load spark knock conditions.
Do you have alcohol fuels available? Over here people with turbo/supercharged engines might use E-85 (85% Ethanol, 15% gasoline, 100-105 octane?), but you'd probably have to run even bigger injectors, and maybe a programmable tuner ECM.
03-09-2017
#5
Registered!!
Thread Starter
Join Date: Mar 2017
Age: 43
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 
