HP/TQ difference from 90mm to 93mm

[Jimmy18E]

Guys

My motor (2.5ss) is out for some mods (GT-3 oil pump & DC-62 Cams in place of the Web Cam 120/104 that were in it) as well as a freshen up. This motor is pretty much maxed out as far as mods go.

I have 90mm cylinders with 10.5 JE pistons in it now; my question is what would be the approximate HP gain if I went with some 93mm Nickies/10.5 JE to bring it to a 2.7SS. It can breathe, all windage mods done with Extreme's twin plug HSR 2.5 race heads.
While the motor is out and apart I am trying to decide if the gain in HP/TQ is worth the jump & $$$ going with the Nickies/2.7ss. It is not a track car but in LTW 71 911 used for back road/DE.

Thanks for any info.

Jimmy

[Flieger]

I thought that you would need to bore the case too much with the 93s, therefore you can only do it on a 3.0 liter Turbo case or one of the Aluminum 3.0 RSR cases.

[Jimmy18E]

Flieger,

No, LN Engineering makes slip fit 93mm cylinders for my 7R case, they are also stronger and don't have the same issues/problems as other 93/2.9 barrels.

I am just curious as to what the jump in HP would be from a 2.5ss to a 2.7ss with all things being equal.

Thanks,

Jimmy

[chris_seven]

I would imagine that the basic torque curve should improve roughly as a function of engine capacity hence an increase of 1.08 times, assuming correct air/fuel etc.

The effect on Horsepower will be similar as this is a simple linear calculation from the torque curve.

The real question is will the increase in piston mass and hence inertia affect the upper rev limit.

If you have to drop 500 rpm, for example, it could negate the cost and only have the same peak horsepower.

The improved torque curve may be a benefit depending on your gearing but it isn't guarantee without looking at the detail of the entire drive train.

[oddmund]

LN Engineering 93mm cylinders are matched to JE forged (light) pistons -http://www.lnengineering.com/pistons.htm - around 395g each - so there will be no need to reduce max rpm. I have the same combination with twin plugs 10.5 :1, DC 40 cams and a redline at 7500. With DC 62 cams 8000 rpm might be ok.

[C.Plavan]

Flieger,

No, LN Engineering makes slip fit 93mm cylinders for my 7R case, they are also stronger and don't have the same issues/problems as other 93/2.9 barrels.

I am just curious as to what the jump in HP would be from a 2.5ss to a 2.7ss with all things being equal.

Thanks,

Jimmy

Ohhhh- You had to post that so I could see it....... I have an extra 2.5L SS race motor in my garage that I was considering selling, and you are telling me I can make a 2.7SS out of it...lol Damn you.

[Jimmy18E]

Chad,

Sorry about that, I am feeling your pain buddy...lol.

If I could sell off my 90mm Mahle cylinders and JE Pistons I think I would go for the jump up, otherwise I will stick with what I have.

oddmund,

How you liking your 2.7ss?
My motor with the Web Cam 120/104 made great power to 7800, then nada but my motor is built for an easy 8K so after speaking with John/DC I am going for the DC-62s with an 8K redline, hope to break into the 240ish rwhp as a 2.5. Would love to go 2.7ss though.

Jimmy

[C.Plavan]

While your at it, why not throw a 70.4mm crank in there for a 2.9L? That would give you some Ooomph per $, and cranks are not that expensive.

[Flieger]

Just make sure to torque those flywheel bolts down tight.

[oddmund]

Jimmy

I am sorry to say that I have only listened to it...so far. The engine went in this summer so we could check for oil leaks etc. Now we are going to remove it to do some body work, paint and new suspension. The pistons have cut outs for DC 80 cams but I have decided to be a "chicken" using the DC 40 - advice from John D. Maybe DC 60 or 62 would have been the best choice - if my cylinder heads could move enough air - 36mm ports inn and out.

I was hoping for 240-250hp or 210-215 rwhp with a power band from 3500 to 7000. Some kind of "2.7RS with more of everything".

Winter is coming earley in this parts of the world so I do not expect to be on the road before April next year - I will let you know then.