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by **hemingway** on Mon Nov 07, 2005 7:13 pm

What compression ratio do you recomendet for 15psi of boost and 75hp of nitrous on RS1800 engine.
Engine will be run with supercharger and nitrous.
I think that 9:1 will be fine with forged pistons and properly ignition setup?
Or do you thing that 8.5:1 will be best.

by **heeman10** on Tue Nov 08, 2005 12:46 am

I was going to say 7.5:1. You could possibly manage 8:1 with good mapping and fuel? Maybe others have input? I'm on 7.8:1 with 12psi and the mappers were a touch concerned about det occurring.

by **sailorbob** on Tue Nov 08, 2005 10:28 am

heeman10 :I'm on 7.8:1 with 12psi and the mappers were a touch concerned about det occurring.

What is it with Fords and such low compression? Many japanese engines run higher compression without problems (even on our lower octane fuel).

by **hemingway** on Tue Nov 08, 2005 2:02 pm

I'm definetly not going under 8.5:1. Hondas run 10.2:1 with 13psi of boost without any problem...
Even stock focus zetec 2.0 run on Jackson racing kit 13psi on stock comp.ratio.

by **FedeArg** on Tue Nov 08, 2005 2:07 pm

sailorbob :
heeman10 :I'm on 7.8:1 with 12psi and the mappers were a touch concerned about det occurring.
What is it with Fords and such low compression? Many japanese engines run higher compression without problems (even on our lower octane fuel).

I was going to say the same thing. The Passat 1.8 T has 8.5:1 and it can run on 95 RON fuel so if Hemingway uses 8.5:1 with a good fuel he could be runing 1 bar without detonation risk.

by **hemingway** on Tue Nov 08, 2005 2:14 pm

I allways use 100 octane fuel.

by **turboboss** on Tue Nov 08, 2005 2:38 pm

hemingway :What compression ratio do you recomendet for 15psi of boost and 75hp of nitrous on RS1800 engine.
Engine will be run with supercharger and nitrous.
I think that 9:1 will be fine with forged pistons and properly ignition setup?
Or do you thing that 8.5:1 will be best.

what management are you running? you can run on 9:1 comp with loads of fuel and more retard. andy nicolls who owns an-racing on his rover 25 he is running a gt35r external gated turbo @ 45psi on standard compression 10:0:1

and 75 shot of nitrous, cost serious money the engine runs I beam steel rods

he wants to be the first one in the country to do a 10s 1/4 fwd

the car geared for 200mph but he had a few problems @ totb so only done 177 so far the car achieved 0.60- 4.1 0-100-7.6 0.150-15.2

by **hemingway** on Tue Nov 08, 2005 4:50 pm

megasquirt...

by **Excursion** on Fri Nov 11, 2005 1:26 pm

Zetec heads don't like high compression, apparantly...

by **FezzR** on Fri Nov 11, 2005 2:42 pm

Excursion :Zetec heads don't like high compression, apparantly...

care to elaborate on why they dont mark, is there a common failure on them you know about?

by **hemingway** on Sat Nov 12, 2005 3:17 am

I dont understand that "care to elaborate?"
ZEtec head is not reason why comp ratio must be lower than 10:1 like original does. It is about knocking problem.
Ahhhh you dont help me much.... but thanks anyway.

by **FezzR** on Sat Nov 12, 2005 11:26 am

hemingway :I dont understand that "care to elaborate?"
ZEtec head is not reason why comp ratio must be lower than 10:1 like original does. It is about knocking problem.
Ahhhh you dont help me much.... but thanks anyway.

edit my post to hopefully make more sense,

by **hemingway** on Sat Nov 12, 2005 11:53 am

I agree with you FezzR. People yust talk something but they dont have real explenation of problem.
Ayway I will share my experience with you when I began with my project.

by **Excursion** on Sat Nov 12, 2005 1:17 pm

hemingway :I dont understand that "care to elaborate?"
ZEtec head is not reason why comp ratio must be lower than 10:1 like original does. It is about knocking problem.
Ahhhh you dont help me much.... but thanks anyway.

The chamber design and squish area is the main reason the engine doesn't like high compression. The onset of knock is directly linked to these. I can't elaborate anymore than this as I don't have first hand experience of it going wrong with a high compression zetec turbo, but I fully trust the source of this info! Having you said that you intend to run 100 octane race fuel, I have no experience at all of how a Zetec behanves with that and I doubt anyone else here does.

In response to your original question, I would stay at 8.5:1. There really is little gain going for a high compression Zetec turbo engine, the real world gains are small.

by **hemingway** on Sat Nov 12, 2005 4:48 pm

heeman10 : I'm on 7.8:1 with 12psi and the mappers were a touch concerned about det occurring.

How much bhp do you have on your monster machine?

by **heeman10** on Sat Nov 12, 2005 10:31 pm

Not a great deal, 220ish? Maybe more, maybe less, I haven't had a chance to give it a power run.

by **alti** on Sun Nov 13, 2005 1:51 pm

hi!

my cossi has a cr of 8:1.
and i can run 25psi without any problems,

whats the reasen that zetec turbo use so less cr?
perhaps you need a good map with a knock sensor?
to run like hondas with 10:1 and 15psi?

the focus rs is near the same as the old zetec,
and you can run 20psi with the stock engine.
i couldn´t believe that the head is the weak point,

but perhaps someone can clear me up!

thanks alti

by **hemingway** on Sun Nov 13, 2005 10:55 pm

Now I decide to make 8.5:1 comp. ratio and we will see if it will be any problems.
By the way... do you know anyone who make supercharged Fiesta RS1800 on this forum?

fiestaturbo.com

What comp. ratio on rs1800 supercharged engine?

What comp. ratio on rs1800 supercharged engine?

Re: What comp. ratio on rs1800 supercharged engine?

fiestaturbo.com

What comp. ratio on rs1800 supercharged engine?

What comp. ratio on rs1800 supercharged engine?

Re: What comp. ratio on rs1800 supercharged engine?

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