Turbo Zetec

iTrader: (1)

got a mate who's gt4 runs a gt3076r and 8.5:1... and he's thinking of making it higher comp! had no problems whatsoever so far at 1.1 bar

mine (on a gt3076r or gt3082r will be roughly 7.8:1 when finished hopefully

Red16

go both ways eh Mark also pm sent

MD Cos thats exactly my point

pete mcrash

iTrader: (1)

is it not just how different engines are designed..????

marco polo

iTrader: (1)

Franco

you having internal or external

lead_foot

iTrader: (1)

Sales of GT30's have sky-rocketed!

Jump on the bandwagon, Yee Haa!!!!

Red16

dunno, not trying to stir things up, just always wondered when reading car specs.

Stavros

What do you fucking expect at only 1.1bar FFS

Not many of them at that compression run over 1.5bar on pump fuel though. Might run 2bar+ on race gas etc on track etc tho.

And a LOT of people bullshit about what comp a car is. I know for a fact some big name Skyline tuners run comp in the mid 7s and keep it quiet or blatantly lie.

And standard compression pistons DONT always mean standard compression

And you can run more boost, but less ign, and ign generally gives more power than boost after a certain level.

And you can also get away with more with wilder cams, more headwork, and bigger exhaust housings.

And all that lot is exactly why engines need to be specced as a whole, as pic some bits of a low comp engine, and some of a high, and you will end up with a properly shit engine.

Mark Shead

I run 8.5-1 on the Evo's with a GT35 running 2.5bar boost on pump fuel.

Mark

Mark Shead

Stavros

Also I am just doing a Evo with a GT40 and above 8.5-1 on pump.

Mark

Red16

but 8.5:1 compression pistons should mean 8.5:1 comp pistons surely!

i know what youre saying Stavros but theyres just far too many jap cars (more than a few on the MLR) running this kind of c/r with say 1.5-2bar boost on pump fuel, they cant all be lying.

Edited to say - isn't Gary@APT running 1.8bar and 8.5:1 with fantastic results?

_DAN_

/
Doesn't the skim of the head change the situation there?

rapidcossie

The comp ratio on my car is so low that people on here would say it must be shit, yet is one of the most powerful and responsive like for like.

Red16

yeah it makes the comp ratio higher

Stavros

Enlarged combustion chambers

And yeah, im not saying they all lying, they not, not even a majority of them, im just giving the various reasons.

Also engine/head/piston design plays a part, just like the cams/turbo/etc i already mentioned.

Skyline GTR engines, and maybe Evos too, can run a shocking amount of ignition compared to what cossies seem to be able to.
Infact GTR engine it seems, if ran at ign numbers you would normally consider normal and safe, are shite and run dissapointing numbers.

There more than one way to do anything.

Red16

yeah thats true, never thought of enlarging the combustion chamber... but lots run standard heads so that would eliminate that.

this is more at what i was trying to get at, but i guess its not a simple one line answer as to why this is the case

NEIL A

iTrader: (6)

Must all be to do with the fact the whole engine has been speced to work with the low comp. Im sure that Neil from Carwise was on something stupidly low aswell like 6.8:1 and it went well too

Franco

iTrader: (2)

Going external route now Marco, as thats what Martin has said will suit the build

Cant bloody wait!

rapidcossie

aint 6.8 high comp?

Mike Rainbird

iTrader: (3)

You can't compare differently configured engines. The Evos run a much smaller bore size than the Cossies, and the smaller the bore, the higher the compression you can run.

Chip

iTrader: (3)

The evo cylinder head shape also appears to be a little better for avoiding detonation too.

RWD_cossie_wil

iTrader: (9)

We do this topic every 6 months, all we ever get is Sheady going 8.1-15.1 , Rainbum going anything over 8.1 is a timebomb , and lots of from people, why even bother replying if you are not going to tell us what you are running?

Talk about secret squirrel

On a different tack, I will be running a CR Engineering T38 on my escort cos, looking for anything around 420BHP, but I was hoping for a nice fat midrange but I am a bit worried now . Engine will be 7.4:1 (cc'd) , with a std exhaust cam and a BD14 inlet, with mild headwork, having spoke to my tuner I have every confidence his prediction of not a lot more lag than a .48 T34 will be true, as the engine has been specced with this turbo in mind. If I don't like it I might be forced to try a GT30

I also have a GT35 sat under my bench, now a few people have swapped back to the GT30 from this, is the general opinion that a GT35 is a bit too big for a 2.0 YB to be nice to drive on the road?

Chip

iTrader: (3)

QUOTE OF THE MONTH!

MAD Ade

iTrader: (1)

Will be interested to see what mine's like on the road. The new manifold has transformed the power from the GT35, can't wait

Porkie

iTrader: (1)

solid lifters now bastard!

Mark Shead

I would easly run stock compression on that spec or above, I have a stock engine running a ported head maxing out 560cc injectors running 2.1bar boost and that version turbo works very well on it.

Mark

marco polo

iTrader: (1)

oh cool

Franco

iTrader: (2)

Porkie

YOU READ MY MIND! Oh well that'll cheer Martin up no doubt!

marco polo

All this fucking around trying to decide on what turbo to run Marco, just seemed easier to fork out a little bit more and go external!

Mike Rainbird

iTrader: (3)

Mark,
What sort of ignition values does the Autronic allow you to run at that kind of compression? The only reason I don't (and AVA) like high compression, is the reduction in ignition you have to run to compensate for the high compression. On a heavily used track car, the heat this puts into the engine is immense, so the benefits of high compression are negated by the resultant down-side of the ignition being retarded compared to where it could be with a lower compression. Personally, I would rather run the engine cooler with us much ignition advance as I could have and loads of boost, rather than loads of boost and lots of retard (by comparison) to compensate.

Low compression allows you to run 16-20 degrees on the top line, where if the compression is too high, this can be reduced to single figures....

rsnissan

iTrader: (9)

Thanks for the replies, quite a lot to digest.........................

Loving Doug's post that Porkie quoted, that's pretty much the stomping ground I was after with the build. Although on more of a tighter budget I'd guess

RE the solid lifters, is it worth fitting these in a relatively standard build? I am guessing this will allow for higher RPM but what else would you require for this?

Franco what is the rest of your spec I would got for an external gate as well while I was at it so yours sounds interesting

Chip

iTrader: (3)

Solid lifters really arent that needed, you can see 8Krpm on the hydraulics.

For a budget build I wouldnt bother as its money that could be spent elsewhere.

Franco

iTrader: (2)

rsnissan

Reyland endurance spec Andy! <---- Just for big will

I'll Pm you all the spec mate, got it somewhere...

Franco

iTrader: (2)

So in essence Chip I'd be getting approx 600-900rpm for an outlay of say Ł400-Ł600 smackers?! (new cam, lifters, shims etc)......

Chip

iTrader: (3)

You can rev to 8000+ on the hydrualics.

Revving too 9000 instead would have me wanting to change the conrods as well personally, so I disagree with the figures you are mentioning when applied to a nearly standard engine like the one this thread is about.

Martin-Hadland

iTrader: (2)

You can see 8k on hyd and I have done this in the past but believe me the engine feels completely different on solids at that sort of rpm.

Like you said if it's budget build then maybe not worth it but it is worth doing at the time of engine build rather than thinking about carrying out the conversion at a later date. So what I'm saying Mr Franco is if we are doing it let's do it NOW not after it's fitted into the car.

Rod-Tarry

Mark is making mine higher compression after the development work on the Dyno. mine was 7.4:1. Im not technical but im sure Mark will say what was going on.
It runs unristricted boost 2.5bar all the way .
Was on Hydraulic lifters @ was rev'ed to 8.3k regularily including pulling 8.3k in 5th (210.2mph). Its now on solid lifters just in case we have the Power to pull past 8.3 in 5th which is 218mph on my present gearing.

Chip

iTrader: (3)

Martin, on hydraulics you of course run the risk of losing valve lift at the most important time, high RPM, so I totally agree with you that they are worth doing in a big spec build, was only for this application (cheapy cheapy) that I was saying the limited budget available would be better spent elsewhere (like a decent rear diff for example)

Chip

iTrader: (3)

At 8.3K I suspect you were losing power due to the hydraulics, as I reckon the valves were no longer following the desired profile.

foreigneRS

don't forget that solid lifters will require maintenance as well to maintain valve clearances whereas hydraulic don't

Chip

iTrader: (3)

At regular use of 8K rpm and just above, I would argue that it is in fact the other way around!

Martin-Hadland

iTrader: (2)

100% true, I know that from experience.