MX5 NC 2.5 impressions
Discussion
Some time ago I bought this reasonably cheap:
I'd seen it on FB for too much money and it looked a bit dubious.
Then the chap advertised it on Ebay, but it got bid up to silly money and the idiot that won the auction hadn't read the description properly, he was in Ireland and couldn't pick up for a while. The owner needed it taking away immediately.
It went through an Ebay auction again so second time round I won it. I hooked up the trailer and went down South to pick it up and drag it back up to the grim wastelands of The North.
The owner was a cop and he'd been recorded being a bit naughty so was forced to quit. His GF chucked him and he was upping sticks and heading off to Oz.
I took the ridiculous wheels off and got decent money for them, then I took the new Teins off and sold them too.
I got stuck into the rear of the cills where they normally go:
Rear and front sub off, suspension arms partially unbolted, partly cut off, whole lot shotblasted and painted in Epoxy mastic, worn bushes removed and replaced with Powerflex Black:
I purchased a 2.5L engine, got some oversized juicy high CR forged pistons:
[url]
New rods:
Put a deck plate on and had the block bored to suit:
|https://thumbsnap.com/akkhgiPF[/url]
When you use a deck plate and your knowledge you can ignore the manufacturers clearances and bore it tight. The fit is far more precise, no piston slap on cold start up.
Obtained some medium (ST3) cams, did some mild porting to the head, recut valve seats etc.
Keyed the pulleys to the crank as they're floating and known to slip.
Gearbox was treated to some new metal bushes in various places (plastic one are imprecise and known to fail).
It picked up the nickname Hitler along the way:
I'd seen it on FB for too much money and it looked a bit dubious.
Then the chap advertised it on Ebay, but it got bid up to silly money and the idiot that won the auction hadn't read the description properly, he was in Ireland and couldn't pick up for a while. The owner needed it taking away immediately.
It went through an Ebay auction again so second time round I won it. I hooked up the trailer and went down South to pick it up and drag it back up to the grim wastelands of The North.
The owner was a cop and he'd been recorded being a bit naughty so was forced to quit. His GF chucked him and he was upping sticks and heading off to Oz.
I took the ridiculous wheels off and got decent money for them, then I took the new Teins off and sold them too.
I got stuck into the rear of the cills where they normally go:
Rear and front sub off, suspension arms partially unbolted, partly cut off, whole lot shotblasted and painted in Epoxy mastic, worn bushes removed and replaced with Powerflex Black:
I purchased a 2.5L engine, got some oversized juicy high CR forged pistons:
[url]New rods:
Put a deck plate on and had the block bored to suit:
|https://thumbsnap.com/akkhgiPF[/url]When you use a deck plate and your knowledge you can ignore the manufacturers clearances and bore it tight. The fit is far more precise, no piston slap on cold start up.
Obtained some medium (ST3) cams, did some mild porting to the head, recut valve seats etc.
Keyed the pulleys to the crank as they're floating and known to slip.
Gearbox was treated to some new metal bushes in various places (plastic one are imprecise and known to fail).
It picked up the nickname Hitler along the way:
Fitted some 17 x 8" Enkies which would take a 225 - 235 tyre, bigger brakes, proper oil pressure gauge, a roll over hoop, a set of Meisters. The engine got bigger injectors, a 1.8" manifold, lightened steel FW and a few other things I forgot 
took it to the dyno for some mapping:
[url]
|https://thumbsnap.com/UVRnmGVN[/url]
I retained the original inlet manifold, it has it's pros and cons. It made 225 bhp and 205 ft/lbs torque on an honest dyno so is up by 85bhp and 65 ft/lbs from a 2ltr.
So what is it like?
Well it's bloody rapid, but in more detail it's very, very strong in the mid range.
The cams and lightened FW have knocked the edge off the low RPM grunt and driveability, the OEM intake manifold has reduced the top end somewhat. The high CR brings everything to the party from low rpm, through the midrange, top end and good MPG, but requires 99 Ron fuel.
On the graph the bhp carries on going up and up to the redline and the torque is pretty flat. It would do another 25bhp if it had throttle bodies.
So I took it to the track:
It does fulfil two roles and is both a good road and track car.
The 225 NS2R tyres were woeful, I won't be taking those to the track again. The 2.5 creates too much torque for them, but also there was not enough grip in the bends.
took it to the dyno for some mapping:[url]|https://thumbsnap.com/UVRnmGVN[/url]I retained the original inlet manifold, it has it's pros and cons. It made 225 bhp and 205 ft/lbs torque on an honest dyno so is up by 85bhp and 65 ft/lbs from a 2ltr.
So what is it like?
Well it's bloody rapid, but in more detail it's very, very strong in the mid range.
The cams and lightened FW have knocked the edge off the low RPM grunt and driveability, the OEM intake manifold has reduced the top end somewhat. The high CR brings everything to the party from low rpm, through the midrange, top end and good MPG, but requires 99 Ron fuel.
On the graph the bhp carries on going up and up to the redline and the torque is pretty flat. It would do another 25bhp if it had throttle bodies.
So I took it to the track:
It does fulfil two roles and is both a good road and track car.
The 225 NS2R tyres were woeful, I won't be taking those to the track again. The 2.5 creates too much torque for them, but also there was not enough grip in the bends.
Edited by Evoluzione on Sunday 6th June 22:40
Thanks for the comments, briefly:
The wheel and tyre sizes are in the text.
These things are not simple, nor cheap, but then it's all relative. That is just a very quick and simple summary of a lot of work and expense.
The engines usually come from the US.
It is now a car which you can overtake in with ease, whereas before it wasn't. Usually it's a case of hanging back, building up speed and redlining it whilst crawling past.
Now you just drop a cog, nail it and 3 seconds later you've dispensed with 2 stragglers following a HGV and are quite some way safely down the road.
It's great fun, but you really do have to respect that torque. It comes in unheard and unseen then BAM, you're facing the other way if you were caught napping with the DSC turned off.
It's true that a turbo would do the same, if not more, but they're complex and often fragile. I wouldn't take a turbo car to a track without it having a heck of a lot of extra work done to it.
I hate creating road and track cars, they're a bit s
t and expensive, but this one does both roles reasonably well. Just not as well as it would have done either one on its own.
The wheel and tyre sizes are in the text.
These things are not simple, nor cheap, but then it's all relative. That is just a very quick and simple summary of a lot of work and expense.
The engines usually come from the US.
It is now a car which you can overtake in with ease, whereas before it wasn't. Usually it's a case of hanging back, building up speed and redlining it whilst crawling past.
Now you just drop a cog, nail it and 3 seconds later you've dispensed with 2 stragglers following a HGV and are quite some way safely down the road.
It's great fun, but you really do have to respect that torque. It comes in unheard and unseen then BAM, you're facing the other way if you were caught napping with the DSC turned off.
It's true that a turbo would do the same, if not more, but they're complex and often fragile. I wouldn't take a turbo car to a track without it having a heck of a lot of extra work done to it.
I hate creating road and track cars, they're a bit s
t and expensive, but this one does both roles reasonably well. Just not as well as it would have done either one on its own.
Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff