Piston Help

[Hutch]

I am looking for a company that can supply 89.5mm forged pistons with a 7.5:1 CR for the 24de engine. I know you are all wondering why so low, well basically the UK fuel is expensive and crap. To be able to run the correct timing @ 1.5 bar without det I need to lower the compression ratio right down.
Please can anyone help ?
Many Thanks
Hutch

[supakat]

Your tuner should have retarded the timing more. If this is what he is saying why the engine failed, then get a new tuner. A built motor is as reliable as the tune. If you cannot find anything lower, then get a thicker hg to lower comp.

[adamky]

There's no need for special low compression pistons when you can simply retard ignition timing. What am I missing here?

[Hutch]

Im lost, I built a spot on engine and it lasted 1 day before the plugs melted to death. I now have to remove the engine and find out the extent of the damage caused. Mapper said that the extremely retarded ignition caused the extra heat and melted the iridium 8's ???
Hutch

[NateDogg]

I would try BKR8E instead.

Wiseco can make you some custom pistons.

[Hutch]

I did have bcpr7es ngk plugs fitted I might go back to them.

[supakat]

Too much retard will have unburnt fuel stay in the cylinder which loses power, overheats, i.e. higher cylinder temps which melt electrodes as your tuner stated. Hence your plugs are fouled. Can you post a timing map of your tune? We generally reduce timing 1:1 for every psi. You can start from 25* and reduce from there. How many KA24DE's are over there in UK?

[supakat]

I am posting this here to show others what were talking about.

These are the plugs I removed Saturday after a severe lack of power. Never had this before, Any thoughts on fault much appreciated.

Hutch

[Hutch]

Just about to put up my timing map, hopefully it will make sense.

[Hutch]

Hutch

[Hutch]

[Hutch]

First picture is a suggested ignition map, second is mine :-/
Hutch

[Hutch]

Too much retard will have unburnt fuel stay in the cylinder which loses power, overheats, i.e. higher cylinder temps which melt electrodes as your tuner stated. Hence your plugs are fouled. Can you post a timing map of your tune? We generally reduce timing 1:1 for every psi. You can start from 25* and reduce from there. How many KA24DE's are over there in UK?

Running 22psi 1.5Bar no other KA24DE-T in the UK that I know of.
Hutch

[supakat]

Full boost is when?

[Hutch]

Between 2500 and 2800 if I remember right but I only had it back from the mappers for 1 day before it blew the plugs and started knocking. When I inspected the big ends and mains the oil I removed smelled badly of fuel.
Hutch

[supakat]

Yea, the unburnt fuel mixed with oil, thinned out the oil, and spun a bearing most likely.

[Hutch]

I already checked the bottom end and mains, no damage. Think the small ends are gone, will not know for sure until I drop the engine out again and strip the pistons out.
Hutch

[supakat]

Oh ok. I was wondering cuz I thought you mentioned that before. So issue points now to cylinder bore. You said you heard knocking. Maybe the electrodes did not expel and are sitting on top of the pistons or something crazy.

Full boost 22psi @ 3K, timing was negative timing. I did this in Excel but kinda hard to paste into php without it construing text. You can follow it though.

Code: Select all

	    3150	3500	3800	4100	4450	4750	5100	5400
24.4	-2.2	-1.9	-1.5	-0.8	-0.1	2.3	 3.4	 4.1
23.74	-1.82	-1.58	-1.15	-0.49	0.21	2.55	3.65	4.49
23.08	-1.44	-1.26	-0.8	-0.18	0.52	2.8	3.9	4.88
22.42	-1.06	-0.94	-0.45	0.13	0.83	3.05	4.15	5.27
21.76	-0.68	-0.62	-0.1	0.44	1.14	3.3	4.4	5.66
21.1	 -0.3	-0.3	0.25	0.75	1.45	3.55	4.65	6.05
20.44	0.08	0.02	0.6	1.06	1.76	3.8	4.9	6.44
19.78	0.46	0.34	0.95	1.37	2.07	4.05	5.15	6.83
19.12	0.84	0.66	1.3	1.68	2.38	4.3	5.4	7.22
18.46	1.22	0.98	1.65	1.99	2.69	4.55	5.65	7.61
17.8 	1.6	1.3	2	2.3	3	4.8	5.9	8

[Hutch]

So far I'm going to get new rings, small ends just in case and a 1.5mm head gasket just to lower the compression slightly. I think it will need a tune again after but it will be ok to drive up to the garage on the original map ?
Hutch

[supakat]

What do you mean by small ends?

You can drive on reg map, just don't boost. The timing map needs to be redone. Atmospheric should be around 28*, not 20*. The first cruise/vacuum map looks better but the 0 psi range can be bumped down two degrees if at most.

[Hutch]

Small end bearing, must be where the knocking is.

[adamky]

That's a lot of boost for pump gas. Most people have to keep it at 18 psi or less to avoid detonation during warmer weather, even on built motors and 91 octane. Our heads are not very detonation resistant, and we don't have much of a knock detection system like some 4 cylinders do.

You mention that full boost comes on very early... before 3000 rpm. For that to happen, you must be running a pretty small turbo. That means it is generating a lot of heat.

You definitely need to redo your timing map. When you get the new one back together, don't run so much boost with that turbo. Unless you get better gas or run meth injection, I'd keep it under 18 psi.

[Hutch]

I am running a 30-76r garrett, also running 97 Ron with meth injection.

[Hutch]

Full torque @3400
Hutch

[supakat]

Lbs per minute: 37
Pressure Ratio: 2.7
Puts him almost off the 78% efficiency island. Anymore boost and it could be counter productive.

[NateDogg]

You need a new tuner or do it yourself.

[adamky]

I didn't realize you were running good fuel and meth already. It sounds like the only thing that could have caused this is the tune.

[NateDogg]

For reference, I ran 14* timing at 28psi on 94 octane and 100% meth on a similar turbo. Never melted anything and it lasted for years.

[Hutch]

Are you all in agreement, the map is poor ? I have to pay out for yet another strip down and rebuild. I have spoken to the tuner and he said it's not the map.
Having said that I wanted to just get in and drive my van, it's very disappointing that you all say the tune is at fault.
Hutch

[supakat]

Yes, the map is poor. The first map would be perfect for the fuel you are using. I ran 20* at 20lbs on corn. Why would a tuner retard the engine that much? I am guessing he does not have much experience with KA's.