Building a 3.0L engine

Is there any way of raising the compression ratio above 9.5:1 on an even fire 2850 cc atmo engine without machining the head down ?


10.5:1 would be good

could you lower the combustion chamber area ? (inserts or welding)

are there any high comp pistons available?

Take a mil off the heads and run high lift cams, and pocket the pistons by a mil. Easy peasey

Actually it IS easier than you might think. You will have to re-time the cams ( which you need to do anyway when running better cams) and you MIGHT be able to get away without pocketing but you may not be able to run as much advance on the cams.

Been to see my engineer friend and he reckons the best way to get more is to strengthen up the bottom end and have a high comp running no more than 1 bar on the standard turbo!

Tell him the bottom end is the last of his worries. The fact that's its an old, mild lifted, very retarded 12v with a pissy small turbo and a crap intecooler. The bottom end will take up to 400hp an the longer stroke engines, no idea what the Z7U crank will take but suspect it'd be more but of course it'll be tougher to hit the same targest with a shorter stroke.

Obviously a standalone ecu is required.He has never heard of adaptronic and was concerned that it may not be quick enough to react to what the engine is doing, as compared to say an Omex or Pectal system.

Adaptronic is every bit as fast as any other modern standalone system. The trouble used to be getting an ECU to understand the standard trigger pattern. The adaptronic sort of does but its ignition table figures will be fairly wildly wrong in the higher ranges. Omex apparently will understand it.

The thing about John was a joke......hes someone from the US who claims to have a 400bhp PRV....until David sorted him out that is!!

He still gets thrown around as an example in the DeLorean world. Much to my irritation Only last week someone popped up claiming to have found a 3 litre odd-fire that pushed 210 at the heels naturally asp through K-Jet.

Chinny reckon.

.. as a matter of interest, how much more portential does the A610 engine have for tuning over the GTA... given its even fire, 3 litre etc...?

(they're both even fire)

The 3 litre engines have fatter pistons on a longer stroke with higher lift cams with better duration and bigger valves. There's a lot more difference than just 500cc.The pistons are also oil cooled, FWIW

Adaptronic is every bit as fast as any other modern standalone system. The trouble used to be getting an ECU to understand the standard trigger pattern. The adaptronic sort of does but its ignition table figures will be fairly wildly wrong in the higher ranges. Omex apparently will understand it.

Que??

Yes, as suspected, Tony's ignition map had to be fairly heavily modified in order to work correctly on the Renault pattern as opposed to the 36/1 pattern. As suspected, the ECU resets correctly and therefore meters the correct fuel but its positioning is inaccurate and has to be fudged in the ignition map. Omex will read the 66/3-with-two-ffat-teeth pattern. Apparently.

When did he have that done?

Yes, as suspected, Tony's ignition map had to be fairly heavily modified in order to work correctly on the Renault pattern as opposed to the 36/1 pattern. As suspected, the ECU resets correctly and therefore meters the correct fuel but its positioning is inaccurate and has to be fudged in the ignition map. Omex will read the 66/3-with-two-ffat-teeth pattern. Apparently.

But seeing as the Adaptronic can work with any value that the user inputs, so you can have the ignition map exactly correct to the real event if you really wanted to..Its just the job of jiggling the figures on the trigger setup to suit.

You may find the OMEX 710 can work with the Renault trigger, but then it is their most expensive unit at £1500..

Presumably now that Tony's igntition map is sorted he has more top end power?

I could set the Adaptronic up to be exactly right for the angles if you like Martin.

End of the day, an ecu doesnt have to look at the exact 'Renault trigger' to have an accurate reference. It just needs to find a repetative sequence so it has a base trigger to fire off. You could tell an ecu to ignore all of the teeth, and treat it as a flywheel with 3 'triggers' (say it just looks for a wide voltage swing (being the double tooth and the double gap)

For all we know maybe thats what the original ecu does - think of the fat tooth and the big gap just as one 'oversize tooth and a gap' - so maybe it just looks for 3 of those and ignores the rest....????

Is there any way of raising the compression ratio above 9.5:1 on an even fire 2850 cc atmo engine without machining the head down ?


10.5:1 would be good

could you lower the combustion chamber area ? (inserts or welding)

are there any high comp pistons available?

Take a mil off the heads and run high lift cams, and pocket the pistons by a mil. Easy peasey

Actually it IS easier than you might think. You will have to re-time the cams ( which you need to do anyway when running better cams) and you MIGHT be able to get away without pocketing but you may not be able to run as much advance on the cams.

Except you would have to worry about the inlet manifold lining up again across both heads, elongating the holes in the timing chain cover, skimming the top of the timing cover so the rocker covers still fit, oh and hoping on an evenfire that the dizzy oil seal in the timing cover doesnt leak oil into the dizzy cap as you have just made the drive shaft 1mm off centre to the seal, pushing on one side and distorting it, along with the fact that your rotor arm is now spinning off centre to the dizzy cap too, and seeing as there is about a 10th of a mm between the tip of the rotor and the electrodes, will smash into half of them....

..or you could get round it by cutting up your covers and welding them back together..

Its just the job of jiggling the figures on the trigger setup to suit.

No, it's definitely not. Trust me on this. The higher the value in the map, the greater the offset.

I'm not arguing the Adaptronic is good value, I've had three off you so far, and would use it again - but I'm fast running out of flywheels and they're *slightly* pricey from Renault! The next thing will be a simple 36/1 trigger on the end of the cam

On the subject of these pistons - have you ever supplied a set of 93mm turbo pistons? Do they mate up to the stock conrods and gudgeon pins? Do we rely on the stock liners? Why didn't you pipe up sooner - I went and bought the skyline instead of doing my engine build because I couldn't get pistons!

I could set the Adaptronic up to be exactly right for the angles if you like Martin.

Off a stock flywheel? I bet you a set of turbo pistons you can't. When Peter's got his back up and running, read off the figure in the map for, say, 5000rpm @ 100kPa and check with a digital timing light. I bet you find between a 5 and 10 degree offset

End of the day, an ecu doesnt have to look at the exact 'Renault trigger' to have an accurate reference. It just needs to find a repetative sequence so it has a base trigger to fire off. You could tell an ecu to ignore all of the teeth, and treat it as a flywheel with 3 'triggers' (say it just looks for a wide voltage swing (being the double tooth and the double gap)

No, it triggers off a falling edge - although you could potentially configure it to look for a time base correction (one pulse is twice as long as all the others) and reset on that - that's config Andy would have to do and include as a special case in the software.

The reason for all the teeth is better resolution. The more information you give it, the more accurate its operation. That said, I know of at least one popular ECU that relies simply on a single reset tooth per period.

Except you would have to worry about the inlet manifold lining up again across both heads, elongating the holes in the timing chain cover, skimming the top of the timing cover so the rocker covers still fit, oh and hoping on an evenfire that the dizzy oil seal in the timing cover doesnt leak oil into the dizzy cap as you have just made the drive shaft 1mm off centre to the seal, pushing on one side and distorting it, along with the fact that your rotor arm is now spinning off centre to the dizzy cap too, and seeing as there is about a 10th of a mm between the tip of the rotor and the electrodes, will smash into half of them....

..or you could get round it by cutting up your covers and welding them back together..

1) No, there's plenty of slop in the timing cover mounts to allow for a mm of variation at the head - go look at one. There's plenty of room in the intake manifold mounts to account for a mm variation too. Just use decent O-Rings
2) the rocker covers seal fine if you use rubber gaskets or RTV
3) The question was directed at an atmo (althgouh he said "even fire atmo" I took this as a mistake?) so the even fire oil seal is a moot point, and as I said, you need to time up the cams manually afterwards to account for the variation. This means pressing out the locking pin in the sprockets and using a dial gauge and degree wheel and locking them down with the bolt. Trust me, it works, got the tee-shirt.

All of DMC Houston's Stage II engines have a mm taken off the heads. Kevin @ Gto went even further, IIRC.

He has an even fire as in a Z7W.

And don't even mention to me again that you take the keyway pin out of the cam and just rely on the bolt in the end of the cam to hold the sprocket in position