4G18 sohc to dohc conversion( in CS3) engine knock

[Float]

I have done this project in my cs3 2005 lancer(local). I am currently experiencing engine knock (spark knock) checked timing three times,I know i have increased compression so changed spark plugs to proper heat rated ones ( bk5re)the previous ones where from a GDI engine (double tip)and were white so I know the engine is burning lean. I own a scan tool (Launch c reader 7 plus),long term fuel trim 12.6 percent short term fuel trim approx.8 percent, to me this is good air fuel ratio mixture.i also tried bigger cc injectors 210 cc, i saw the the rich mixture on can tool short term fuel trim was 19 percent the ecu u was compensating for the bigger injectors to get back the long term fuel ratio to 12.6 percent despite this it still knocked ,after this I reinstalled my injectors and things were back to normal except knock so i am going to custom make a EGR pipe to the intake and exhaust because the ck2a dohc head does not have exhaust port in head to go to cs intake manifold EGR valve so it has to be done externally. I am doing this because I cannot remap my ecu to delete the EGR. In essence I think the absence of the EGR is causing the lean mixture hence the knock.Anyone who dis agrees please comment need the knock to stop and it happens when the engine is warm or going up hill.posting.php?mode=reply&f=33&t=265061&sid=3ff3be4b5c4586b564d5f80dd8975bd9#

[trini iceman]

Would plug gap contribute to this?

[Float]

yes it could but tried that and it still knocks.Been doing a lot of research though and other people with the CS conversion get the knocking even with adjustable cam gears so I am going to try bkr7e (cold plugs) to compensate for the high compression before i custum fit egr .thanks for reply

[xtech]

Why aren't u remapping and flashing the ECU with new parameters ?

The injector timings are probably off because the DOHC flows more air.

[Float]

viewtopic.php?f=33&t=376048&hilit=4g18 this is why I did not change the ecu parameters "yet" .

[xtech]

U got to be kidding me.

Well something gots to be slightly off in the chamber. Like A hot sharp edge that the ignites the fuel.

Did anybody try to Cool it down with water injection?

[trini iceman]

Did you check the fuel trim under load or just at operating temp idle? You only get the knock or lean situation under load? Is this an engine swap or a head swap? What's the present compression? What's the shape of the pistons in this setup?

[Float]

Head swap. knocking occurs under load or going up hill but did not check fuel trim under load when knocking occurs. Do not know current compression ratio but i guess it is around 10.5 -11 to 1,the 4g92 mivec is 11 to 1 and use bkr6e cold plug I have bkr5e . The piston head is flat(pent-roof head design) compared to ck piston which has a dip like a bowl(semispherical design),and car still is burning lean(white bkr5e plugs),will observe to see if it is lean at time it knocks. I also own a factory manual(Australian model) and concerning spark detonation it says to unplug knock senser and see if ignition is retarded .I did so but ignition remained at 9 to 10 degrees btdc at idle ,drove it and the knock is still there, it also says if it continues to change the plugs to proper heat rated.(I know mitsu never built a 4g18 dohc but was just checking still). (correction 4g15 mpi dohc and 4g18 mpi sohc both used pentroof design)

[Float]

U got to be kidding me.

Well something gots to be slightly off in the chamber. Like A hot sharp edge that the ignites the fuel.

Did anybody try to Cool it down with water injection?

No have no knowledge of how water injection works unless it is to remove carbon deposits from combustion chambers or cool inter cooler and yes i know there is extra heat in chambers trying to understand how it occurs to find the cure.

[xtech]

All I can think of is the engine is
Breathing better an you gots more air to deal with. Add wideband And monitor when it knocks. I am sure water injection or bigger injectors will fix that.

Had the same problem
With a starlet engine when I swap 1300cc block to 1500cc High compression setup added RX7 490cc injectors to fix the knock. Original injectors for the 1500cc engine is 230cc an for the 1300 was 290cc.

Tuned it with a fuel controller an that was it. More air more fuel more power

[trini iceman]

What work was done to the head? What gas you using?

[Float]

I am using what everyone knows as super . No work was done to head just direct swap.Put in bkr6e plugs today and the knocking continues.Thinking of custom fitting EGR next, getting code p0400 (EGR flow) not detected and if this does not work i will have to admit the engine build is prone to knock because of the clash between combustion chamber and piston design .....tell me if this theory makes sense.
The first thing I noticed when i removed ck head is that the piston crown were like a bowl and the 4g18 had a flat head with slanted edge for the valves (4 imprints on the head) so using ck pistons to see if the compression ratio will drop . My spark plugs are still white though(burning lean) tried bigger injectors(denso 210 cc) ,got same result(STFT19%) and decrease in power put in 4g18(BOSCH cdh 210)210cc short term fuel trim was -17% computer richening mixture cause of dirty fuel injecters(definitly not driving good),put back in 4g15 dohc (bosch cdh 165) 165 cc STFT was perfect(near zero 2,3, 6% and 0% of throttle while driving) the knock comes in from 14 to 26 degrees btdc(ignition timing and 9,10,11 degrees at idle), engine temperature about 88 degrees Celsius mostly while driving, LTFT 12% good readings with with 165 injecters but I know they are not the right ones and may be a contributor to the lean burn situation which is evident on the plugs (will observe the new bkr6e) but will work on this. More prominent on my list is trying ck DOHC piston to correct combustion chamber design for total elimination of the knock. will try to give pics of the data stream of the car and put up a video on you tube and send link.

[Float]

Would plug gap contribute to this?

gapped them to .20 inches

[xtech]

So not only is the engine breathing better u coupled it with semi high-compression pistons.

U could Try the egr but it won't help unless u use a egr cooler as well. If u wanna keep those flat top pistons buy a water injection kit or reprogram the ECU to adjust ign and fuel injection timings where it knocks. An most important u will need a wideband to match with your data logs

[Float]

Where can i purchase a water injection kit ? What is the average price ? I live in Tobago even it is in trini i will come get it according to price.

[trini iceman]

They sell for around 2500. If you lift the head try cleaning as much carbon as possible from the head chamber and look for burs on the piston caps to reduce hot spots.

[chosen1]

To me it sounds like you should try a higher octane fuel