higher compression - retard timing?

[EPnick22]

rebuilding my engine with 9:1 compression pistons (people are probably gunna moan cause I shouldnt go higher, but yeah ) once its rebuilt and all the cams are back in , valve timing sorted etc, when I put the distributor back in place (in the exact place it was when i took it out) will the timing need retarding due to the higher comp?

[AdamB]

I would retard it until its mapped. I would expect to use a good standalone ecu if running that high, wouldn't trust a piggyback. What pistons are they? Is it 4E? Has the CR actually been measured and calculated?

Edited September 19, 2013 by AdamB

[EPnick22]

theyre wiseco 9.0 compression ratio pistons says on the box, im on the stock ecu, been told by a lot of tuning places that itll be fine, and that itll be more economical and responsive and more torque, but obviously will come with the heat factor so will be running less boost, just wanted to know about retarding the timing, was going to get my tuner to do it for me

[AdamB]

Flat tops I take it? Same as Toff's. Just because it says 9:1 on the box doesn't mesn it will be. You need to measure the combustion chamber volume and calculate the CR.

I hope your planning on upgrading the management to something decent. You can either retard the ignition timing,retard the valve timing or do both. I would set the base ignition timing to something like 7 or 8 degrees BTDC.

[EPnick22]

flat tops yeah, how do i measure the cr? ahh this is more agro than i thought itd be didnt have any plans really to upgrade ecu, whats wrong with using a piggy back?

[The Toffinator]

Yeh they sound like the same pistons i have, depends on headgasket thickness also really, How thick is the headgasket you are using? I Worked my compression ratio out on my 5e and it should be high 8s using a 1.4mm gasket

The compression ratio stated is based on the standard 1.0mm Gasket and an unskimmed head etc

[AdamB]

flat tops yeah, how do i measure the cr? ahh this is more agro than i thought itd be didnt have any plans really to upgrade ecu, whats wrong with using a piggy back?

Assuming its a 4E with 74.5mm bore, 1.2mm headgasket and a stock combustion chamber volume, but you'll have to measure it to be sure and also measure any volume in the bore when the piston is at TDC, although if flat top pistons they should sit level with the deck height.

Your CR would be 9.6:1.

Even with a 2mm headgasket it will only drop it to 9.4:1. If you want somewhere around the 8.5:1 mark you'll need a combustion chamber volume of 45cc.

With a high compression engine, knock is more inevitable, so better control of the ignition and fueling is paramount. What turbo do you plan on running as well?

Edited September 20, 2013 by AdamB

[EPnick22]

so how do you actually measure it? and if my pistons arent 9:1 that means 8.5:1 arent 8.5....? ive sent my 1.2mm gasket back for a 1.4mm in exhange, im getting my timing set up by my local tuner who are evo specialists and also do a lot of starlets, had a word with them today they said itll be absolutely fine providing i get the thicker head gasket and my ignition is set up right, and also run higher octane fuel, running a td04 on low boost. Would I be better with the 1.9mm gasket over the 1.4 i was intending on swapping for? also 74mm bores, not 74.5

Edited September 20, 2013 by EPnick22

[AdamB]

You need a piece of perspex plastic with a hole drilled in at one side. Then smear a bit of grease around the combustion chamber and place the perspex on top. Use a burette and fill through the drilled hole with water and take note of how much fluid is lost from the burette, this will be the volume. You can do the same for the block when the piston is at TDC. 1ml = 1cc.

Never go by what it says on the box, your right 8.5 isnt 8.5 and 6.5 isnt 6.5 either. Its only that CR as to whoever designed them and what setup was used to determine that ratio.

Problem is getting a thicker heacgasket is essentially the crude way of lowering the CR, although it does work.

You can't really run any higher than 98/99 Ron fuel unless you have a local supplier of a more exotic fuel and are willing to pay the price for it. Even with that fuel theres still limitations.

Even with a 74mm bore and a 1.4mm gasket your still going to have a CR of 9.4:1, I think you'll be fine to run upto 12psi of boost depending how efficient your intercooler and turbo is you may be able to run more.

[EPnick22]

so what would the difference be by running a 1.9mm gasket? i only ever put in vpower or bp ultimate anyway, and due to running stock ecu i wont be boosting above 10 psi i dont think!

[AdamB]

A 1.9mm gasket will give you a CR of 9.3:1.

Can I ask why your bothering to spend all the money and effort to build a forged engine if your not going to look for a fair bit of power?

If your going to stick to a td04, you'll be fine to run anything upto 1 bar on a high CR. Im sure Harry from Oz had trouble with his 5E running a 9:1 CR as he couldn't boost past 1 bar due to excessive knock, and that was using a very good standalone ecu, although im not sure what fuel they have over there.

[EPnick22]

Im only putting in the money and effort cause i want a reliable engine, I cracked 3 pistons in my standard engine and the effort it wouldve taken to rebuild it with stock bits that are likely to do the same thing, I had the money for forged bits, so why not? plus its safer on a td04 (even though people do run td04 on stock internals), half of it is just for peace of mind of having a fresh engine, plus can sell for more if i do ever sell the car

[AdamB]

Fair enough, why not!

Whats the car used for? Just fast road use?

[EPnick22]

yeah its my daily, and a little bit of fast use on weekends, i drive it pretty sensibly during day time, lots of police round my area until night time, plus its more exciting when you boost every now and then rather than all the time

[AdamB]

I think you'll be fine with that engine setup, but it will need a good management system to hold it up, or you'll just be losing power all the time as the knock sensor works overtime.

I would even be tempted to use a td05 because it'll be more efficient.

[EPnick22]

so i cant run the stock ecu even at 8-10psi? aswell as having the ignition set up by the evo guys down the road from me?

[AdamB]

The only ignition you can set up is the base timing, and your not going to want to run round with it retarded by 4 or 5 degrees all the time as that will cost you a lot of power.

You could use the stock ecu for running in with the correct AFR's but I wouldn't use it expecting to get power from it.

No point spending on a good engine if it isn't going to be controlled properly, its the most important part. You can pick up Motec M4's, DTA S40's dirt cheap, same price as an EMU and they have much greater scope.

[EPnick22]

when you say dirt cheap, HOW cheap? plus mapping costs, gunna cost me more than the engine build once im done with that, surely itd still move better than a ct9 on boost?

[AdamB]

£500ish. Like I say, the management system is more important than the engine, I would rather have a standalone than a forged engine for that kinda setup.

It'll move alright, how well is another question and not something that can be answered until its done.

[EPnick22]

yeah :/ where would i be able to find one of these ecus + full loom etc?

[TurboTobz]

Theres a dta on the forum with a k20 turbo loom _shaun_'s selling, could be modified for your needs...

[EPnick22]

money money money! something im not in a great position with right now :/ 750, plus fitting and mapping expenses is gunna total to a larggeee amount

[AdamB]

Motec M4's crop up on ebay quite often, DTA's are on there all the time, I believe TD have an S40 they are selling I see on their facebook the other day with a full loom.

Shaun on here is also selling an S60 with a loom.

I would be asking your tuner or local tuning companies what they like to map though as its down to the person with the laptop on how safe your engines going to be. That said DTA's are very easy to map.

Or just send your pistons back and get ones with a dish lol.

Edited September 20, 2013 by AdamB

[EPnick22]

cant send them back, theyve been fitted to rods and the rings are all gapped and on the pistons now, plus a couple small marks on them too so definitely couldnt do that, ah i thought everything was falling into place, seems im spending more and more money and not really getting anywhere, just want my car back on the road and boosting, i dont even care if its no more power than the stock turbo either

[AdamB]

Can I ask whos advice you took on buying those pistons in the first place? They caused Toff a fair bit of hassle but he was willing to get stuck in and work on the combustion chamber to lower the CR.

I didn't even know Wiseco offered anything but 10cc dish until Toff bought some and I worked out his CR and that.