Redblock compression ratios?

[Stavros]

Is there a list anywhere of compression ratios (and ideally combuston chamber sizes) for the usual widely available (in the UK) Redblock engines?

Ie early high comp 360 2litre (10:1?), later 360 2litre (9.2:1?), 2.3 n/a, 2.3 turbo, 2litre turbo, and, err, whatever others there are.

And aside from lowering the compression lots (it seems, anyone know an amount?) is there any other issues with fitting a 2.3 head to a 2litre block? Ie is the bore the same etc etc.

Also, though its pikey and makes the squish are big, anyone used a spacer plate or similar to drop the comp on a redblock?

Basically im after 8:1 or near as damnit (tho i can go much lower if thats easier, but not much higher), not arsed if its 2litre or 2.3, but cheap, so no custom designed pistons, lol.

[volvorsport]

volvo advocated the use of two headgaskets in the Rsport conversion kit .

if youre looking for cheap i suggest that IS the cheapest method

oh and search on turbobricks .

i think all turbos would either be 9.0:1 or 9.3:1 on a 2.3 and 2.0

b21 was 7.5:1 - 531 has the largest combustion chamber

[Stavros]

Any ideas how much 2 gaskets drop the comp?

Read on one of the Turbobricks threads that a .120in thick headgasket will drop the comp about .6 on a Volvo.

Dunno how thick a stock HG is tho.

7.5:1 was the old turbo engines we never got on the UK tho, so no chance of finding one of them really.

[Fuse]

I've got a some sort of list, it's not completely accurate and it's missing some details but there's some info. I don't remember where I found it.

http://koti.mbnet.fi/mtn/Engine%20classification.doc

There are also few people on this Finnish forum who know every detail of every redblock but there are no lists compiled.

Two HG's is kinda ghetto way of lowering the compression, I would stay away from it if possible.

[volvorsport]

and for what reason are we lowering the compression ratio ?

SPM pistons lower it to 8.2:1

if i didnt want spend any money , id keep the std CR - theres no really cheap way of doing it , unless your prepared to do the two headgasket thing - or at least a thicker headgasket .

[Stavros]

thanks for all your help, hopefully from all this i can cobble something together

im prepared to do the headgasket thing or remove the squish pads from the combustion chambers.
neither is perfect, not by a LONG shot, but for a forced induction engine squish size is nowhere near as important as some people think, esp when its purely power and torque is your concern.

SPM pistons? never heard of them but i take it a turbobricks search may help there? lol.

for what reason? superchager running nearly at its rpm limit.

[volvorsport]

boost pressure ?

as long as its tuned correctly 9.0:1 shouldnt be so much of a problem - the motronic engined cars run more than 1 bar chipped . (well some)

[Stavros]

i think it will be more than 1bar TBH, its hard to be sure without knowing flow rates of volvos (maybe as high as 1.5bar if volvo heads flow crap!) as you can only adjust blower rpm rather than boost pressure itself.

blower efficency is piss poor at high rpm like the charger will be running, though a decent intercooler will help cure that, but even though, id prefer a lower comp.

im not a big fan of high comp and forced induction at the best of times TBH, lower comp and more ign gives better results and cooler running anyhow.

gonna have to sling it on MS really, dont trust the turbo managment to handle it, chipped or not.

also if i HAD to lower the boost below what id want as say 9:1 was just too far regardless of timing, its a pain in the arse to do so, unlike on a turbo.

maybe 9:1 will be fine, and TBH i dont mind giving it a go, but got lot more to lose if its too high than too low, lol.

[Fuse]

im not a big fan of high comp and forced induction at the best of times TBH, lower comp and more ign gives better results and cooler running anyhow.

Wohoo, finally someone who thinks like me. Nowadays everyone are talking about high comp turbo engines and how "advanced" those are, even though most of people have never driven a low comp turbo engine which makes real power.. It's kinda funny that people don't know that low comp turbo engine can also be totally street drivable and doesn't require full throttle to get it going etc.. Of course if someone is aiming for some grocery getter which doesn't even boost properly and torque is "smooth", then I can see the point in very high comp. turbo engines, but those are for grannies and such..

I'm pretty sure that you can build engine which has compression around 8 with stock Volvo parts, it's a shame though that you didn't get the older turbo engines which would've have low comp ratio stock. I'll try to dig around and look if I can find what would be the best combination..

[classicswede]

have you considered decking the pistons or even cutting some material out of the head to reduce the compression?

[Stavros]

fuse-
exactly! im glad you know too! im the same, i have experienced it, but people who havent just believe all the rubbish they get told!

people say they want high comp but dont know WHY, they just think they do, or get told they do, either as its fashionable, they listening to others who also dont have a clue, or they are getting ripped off by tuners.

most peoples reasoning for not going low comp is "it makes the car laggy and loses low down power" which frankly, is poo.
lower comp would lose SOME (a small amount) off boost power, but off boost a small capacity car at low rpm hasnt got much power regardless of compression ratio!
and to get good power on the same fuel with higher comp means wilder cams and bigger turbos, which ruin low down power a LOT more than lowering the comp, lol.
also compression has little if any effect on what rpm your turbo spools at either, but wild cams and giant turbos (like all big power high comp cars have) certainly do!

as small a turbo and as mild a duration cam as you can get away with is the way for best drivability, compression ratio should just be tailored for the boost you need to run to get the power you after, and of course the fuel you using.

boost also means TORQUE, show me one high comp engine with say, i dunno, 250bhp per litre on pump fuel that has as much low/midrange and overall torque as a well specced low comp one.
ive certainly never found one.

people say "oooh, but a race car runs high comp" but they on RACE fuel, and only go mega high comp as the restrictors stop them making power other ways!
if WRC rules went restrictorless the cars would be straight back down to compression in the low 7s again even on race fuel, as they would be building 400bhp per litre engines, not 150bhp per litre like at mo!

look at de-restricted (aside from capacity) turbo race engines, so F1 Turbo era, 1970s Indy Car, old LeMans, etc etc etc, and ALL the engines ran the same principle.
mild as they could cams and head, small as they could turbo, compression that was however low as they needed it for the boost they wanted, and LOADS of boost.
and all of them had powerbands or torque figures that was HUGE compared to modern restricted race cars and these high comp low boost setups people keep thinking are cool.

no matter what technology is around, you cant change the laws of physics, lol.



Dai- Yes, the material out the head was the squish pads i mentioned, easy done.
Decking the pistons MAY be possible IF there enough meat on them, no idea if thre is though.
It will increase squish area doing that though, as mentioned earlier, but im not actually bothered.

[Fuse]

Oh and btw. SPM pistons are Sten Parner Motor Pistons, www.stenparnermotor.se Sten Parner is a Swedish Volvo Guru who makes all kinds of nice stuff for redblocks.

[foggyjames]

gonna have to sling it on MS really, dont trust the turbo managment to handle it, chipped or not.

To paraphrase Fuse, finally someone who thinks like me!

The later B230 turbos were 8.7:1...but the difference appears to be in the head (531 on the higher comp ones), as we've just had a '89 ET and a '96 FK in pieces, and the pistons look identical to the naked eye. I was sure the B230ET was 9.3:1, but the only figure I can find at the moment is 9.0:1 for the 1985-only B23ET.

I do like your comprehensive thinking...but...I might be tempted to give it a try with a stock setup before you start worrying about CR too much. What are we going to be seeing at worst...25psi? With a suitable IC and a spot of tinkering with the head (read Somender Singh's 'groove theory'?), you shouldn't have to wind the timing back too far to run that much. Actually having the ability to wind that timing in accurately works wonders, for a start. Some of the guys in the US are making 350-400 wheel torque (lbft) at 25psi on a stock head and 'premium' pump fuel without significant ping problems.

I dunno...I guess it depends on how serious you're getting with this. Probably the easiest way is to drop in a set of pistons, rather than messing with the head. Unless you're an expert at headwork, there's a good chance you'll do more harm in terms of ballsing up the burn pattern and making it a ping-whore than good by lowering the CR.

The other way of looking at it is that you're almost certainly going to be able to reliably make enough power to break most of the drivetrain without lowering the CR

cheers

James

[Stavros]

well thats the thing, it will only be 250bhp tops, im not going for big power on this as i dont need it, ive got much more powerful cars than the volvo, with transmissions that can handle it too (well, a Dodge Viper T56 handles anything!), but as im maxing out the charger rpm (for maximum low down oomph, but also as its one i have the most spares ones, lol) the efficency is shockly poor, so much so im not really trusting an intercooler can totally solve it.

TBH i doubt it will get over 20psi, under 25 for deffo, but the charge temps will be immense, lol.

im tempted to try it stock, but the grief of taking the engine out if it buggers up is something i dont want to do. a little more immediate work and expense pays for itself in less work in the long run!

like mentioned, can knock back the timing enough to keep det at bay, but it makes for a generally worse performing engine than lower comp and lots of ign.

TBH though, im happy running stock CR if thats the only significantly cheap option, but if i have an engine in bits, im 99% ill either skim the pistons a little, mod the combustion chambers, or simply double up on gaskets etc.

wont spend a fortune, if i do that ill do it on a 16v lump and twincharge it, but im part way thru twincharging my 200SX and got the GTR to finish, so no way on gods earth am i doing anything big yet, i need the volvo for fun to keep the stress of finishing the others at bay!

[foggyjames]

Sounds like a plan. I'd go with a 230 turbo bottom end, a 530 head (off any 940 turbo), which should give you 8.7:1 out of the box. If you want more, there's a UK group buy on Turbobricks at the moment for Cometic HGs, which can be ordered in a range of thicknesses...and I'm sure the thicker options will lower your CR quite a way.

cheers

James