I'm pretty sure he was running mist - but not mapped to it, so would not have contributed to power.

The crank as John says certainly isn't a problem, I would be more worried about pistons and rods especially with nitrous.

I remember that list John, it's interesting as certain turbos respond well to differing applications and even engines. The one thing that stands out for me on the coupé is the turbine housing amongst the 28R, 28RS/R and 28RS. The difference between a 0.64 and 0.86 is noticeable in terms of spoolup and top end but peak power and torque is often the same. I do feel that to make the most of a larger turbine housing you really need to increase the limiter by 500rpm to give you that wider powerband and offset the later spool otherwise it's a non-starter. As the turbos get bigger on the coupé I'm sure we will start to learn more

Going back to the turbo question, the other thing to consider is availability, cost and the hassle factor. Taking all of these into account, I can whole heartedly recommend Barbz's RSR, on a standard head I'm making 215 ft/lb by 3k rpm and 288 ft/lb 500 rpm later, rising to 297 ft/lb. Kenno has the same turbo and has got similar results. With a modified head, nitrous etc. someone on here got something like 380 BHP with this turbo. Edit: and the above was with a cat (hi-flow) and on 95 RON.

I agree with JohnS - my crank is standard - there's very little imbalance inherent

The rod and piston assembly is where you need to concentrate - IIRC the stock pistons and rods +/-10grams, thus a 20g tolerance. Mine are within 1 gram of each other - I now have a rev limiter of 7,500, although I rarely use it.

so you advise changing the rods rather than having them balanced and matched?
like i say im wanting to build a strong engine that can handle 400bhp even if i dont use its full potential.
isnt it wise to get the standard crank balanced as a matter of course if your taking the engine apart?it dont cost much to get it balanced.will the std crank take 7500rpm if in good condition?

Beast - I'm on standard rods at over 400bhp, so they will clearly take the strain. However, its not really power that kils rods - its either revs or torque (or both)

Standard rods with standard pistons are close to their limit at about 7,500rpm. I have lighter pistons, so I have a small extra capacity

Also, standard rods have been know to bend at much above 350ft-lb of torque. Most big turbo setups are close to this, especially with so,me flow mods, like headwork. However, nitrous will give you great gobs of torque, so if you're thinking of running gas, you should fit forged rods.

point taken and another £750 allocated

Rich back in a 20VT and chasing that previous 1/4 best! Are you going for a Plus/LE or a good old trusty 20VT?

my previouse best was 13.795 and that was with just boost/filter/suspension mods so dont think its gonna be hard to beat tbh.think a late 6 speed 20vt will be sufficient for me,i dont see the point in me getting a plus just for the side skirts and front lips,not for a few grand extra which i would rather spend on speed mods

Better getting a 5 speed to handle the nitrous.

Ross

yeah i know the 5 speed is a stronger box in general but i want the 6 speed for extra top speed,plus arent most of the faster coupes down the strip 6 speed cars?
must admit my old 20vt was a 5 speed and it wasnt lacing anwhere but i got that to over 6600rpm in top with less than 280bhp so im likely to be hitting the limiter with 350bhp plus nitrous

how much do you want that top speed ? 5-speed pox 5th gear 1000rpm = 39,4kmh . 7000rpm= 275,8kmh 7614rpm= 300kmh. isnt that enough ?

Rod bolts are probably not up to delivering 400BHP at whatever torque IMHO. The rod bolt problem is not an acceleration issue but a lift off issue.

GULP!

Why would lifting off when producing 400bhp be any different to lifting off at 300bhp?

For example, I was running base boost this morning, but I still ran round to the redline - If I lift off at 7,000rpm, the tensile forces on the rods are surely no different to those if I lift off from 1.3 bar?

Am I missing something?

i believe it will be something to do with all the pressure on pistons / rods at 7,000rpm (like 18000lbs) and then the pressure has gone when you lift off, so from a very high load to not much load in a fraction of a second

The rod is being forced in a downwards direction all the time you are accelerating due to positive boost pressure and on the exhaust stroke due to the crank forcing the rod upwards.
When you lift off the differential between the positive force on the piston (the power) and the vacuum force is what is loaded onto the rod bolts in effect for a very small moment. So the more power you have and the higher the rpm the greater the differential applied to the bolts. That's why there is always a need for uprated rod bolts on forged rods and on some other cars with lesser bolts they have to be uprated at a much earlier stage than for us.

On my rounds with the std rods before I used them (and don't forget one of my rod bolts snapped) one tuner told me that even if the rods were up to my requirement the rod bolts might not be as if they stretch even slightly the rod will pretty quickly end up out the side of the block or the top of the engine.

i dont want to rev my car to 7600rpm though
the redline(7000) on a 20vt is 175.8mph but the car runs out of puff before 7000rpm so its better to have a higher gear to drop you back down to 6000rpm and still have plenty of power.plus a 6th gear makes long journeys easier and cheaper especially as im after a road car!

johns-your saying that adding some arp bolts to the std 20vt rods wont be beneficial in any way?

adding ARP bolts would be benficial anyway, especially for high revs but it still won't make the rods up to the spec you want. There have been a number of rod bolt related engine failures (not a lot but enough to be notable).

The rod bolts I have are rated over 30,000PSI or 14% higher than the ARP equivalent So ARP aren't necessarily the best, just the best known!

point taken on that john.
yeah i think best course of action for me would be to bite the bullet and get forged pistons and rods just for piece of mind cos i dont wanna build a nice spec up and have it break first time i hammer it.
zero gap rings-advantages??disadvantages?

Less blow by and higher compression IIRC.

Ross