I am trying to decide what power output I need from a donor car, I am going to be using an MX5 donor which comes with either 90, 115, 130 bhp
The car will only be used on the road so I am trying to determine what is substantial and what is overkill especially if it will cost more me more £££
for a higher bhp donor.
Using this bhp calculator and specifying a vehicle weight without driver of 550kg then I get the following results:
http://www.letstorquebhp.com/calculator.asp
90 bhp = 6.43 secs
115 bhp = 5.24 secs
130 bhp = 4.76 secs
What sort of 0-60 time should I be looking to acheive for a road going car without going OTT?
Not really sure how to answer your question but that's a hell of a tool. What a good idea that is!!
Thanks
Dan
Bear in mind first that this car will be one of the faster things on the road even with a fairly modest 90HP. And probably the fastest thing
you've even driven.
My advice is to worry now more about getting the car on the road, power and 0-60 times after you're there.
Of course thats what you and I should do 
I should probably listen to my own advice as I'm exactly the same as you chasing 0-60 times and I
haven't even got a chassis built yet
[Edited on 7/4/11 by liam.mccaffrey]
90hp more fun as you can use it all without things getting too giddy, our roads are rubbish and over crowded so why have more if you can't use
it.
Making sure the car handles is more useful than lots of horse power
My Locost's crossflow engine gives out around 90-ish BHP - and it's faster than most things on the road, short of 'proper sports
cars' (and it's faster than quite a few of them!).
If you drive a 90 BHP MX-5 - as I have - you will find that it's a nippy little thing, and will go quite briskly. Put the bits into a Locost and
you'll remove at least a third of the weight... power-to-weight is the key here.
And I agree about handling - my top speed is usually legal when I'm out and about, but I don't have to slow down much for corners, which
puts me at a huge advantage against other traffic.
quote:
Originally posted by liam.mccaffrey....Of course thats what you and I should do
[Edited on 7/4/11 by liam.mccaffrey]
but of course there is also the gearing and diff ratio to factor in. Simples... 130!
If you go for the 90 it'll be reasonably quick but there'll be plenty of tin-tops that will beat you away from the lights and if you ever go
for a run with other sevens you'll know about it. You'll find yourself using all it's got most of the time.
...115 and it'll be quick and most of the time have a little in reserve, but leave you wanting more.
...130 and it'll be impresive (although not the quickest thing out there) when you actually show what it's got and it'll have leave
most stuff for dead.
Although it might cost more now, If you can, go for the bigger power. It'll be cheaper than upgrading later in the end. Thats providing
you're set on a CEC. You could always go for the 90, get through IVA, use it for a year and then stick a BIKE ENGINE in!
[Edited on 7/4/11 by adithorp]
quote:
SO what are you doing posting on here? Go and get on with it then!!
BTW, good link Blacktop
[Edited on 7/4/11 by Daddylonglegs]
I know the feling mate, I'm so close I can taste it but everything conspires against me 
Maybe we should try starting a 'show-and-tell' at work? Take the cars in
As far as I know the 1.6 is 115bhp and the 1.8 is 130bhp, with the exception of some detuned 1.6 introduced in/after 1995 which are 88 bhp, so unless
you go out of your way to find a later detuned car you really only have a choice of 115 or 130 bhp. The 1.6 is reconned to be freer reving/nicer
engine. You could fit one from an early mx5, drive it like that till you get used to it, then go the way of mx5 entheusiasts and fit a
supercharger/turbo to get more power. You can get 200bhp+ from the 1.6 with new cams/ecu etc, but I believe with stock internals you get to 150+
easily - probably best to check out some of the mx5 forums for more details.
Regards
Hugh
quote:
Originally posted by adithorp
If you go for the 90 it'll be reasonably quick but there'll be plenty of tin-tops that will beat you away from the lights and if you ever go for a run with other sevens you'll know about it. You'll find yourself using all it's got most of the time.
...115 and it'll be quick and most of the time have a little in reserve, but leave you wanting more.
...130 and it'll be impresive (although not the quickest thing out there) when you actually show what it's got and it'll have leave most stuff for dead.
Although it might cost more now, If you can, go for the bigger power. It'll be cheaper than upgrading later in the end.
You'll be wanting a 2.0 Ltr Duratec then
the answer is easy, the most power you can get in there
then just dont push the loud pedal down as hard when you dont want to go fast
there is no such thing as too much power
^^^^^ what he said ^^^^^^^^, it will have better resale value also.
Must say I'm not convinced by all these computer-generated figures when it comes to 0-60 times. There are so many other factors to consider.
However... a good big'un is always better than a good little'un, so if it was me, I'd go for the 130.
Remember that whatever engine you go for will have lost some of its power over the years. It may have given 130bhp when new, but now... what...
115-120 at best, maybe? OK, if you're going to be completely rebuilding it, then it doesn't matter, but I suspect that's not what you
had in mind.
As someone said earlier, gearing and diff ratio will also affect 0-60 time. And it also depends on how well the chassis can deliver the power to the
ROAD. Flywheel BHP and even BHP at the wheels only tell you so much.
If I were you, I'd try & find a few folks who are prepared to let you have a drive in their cars so you can compare.
Also, have you been in a properly set-up seven-style (say) with 115bhp engine up front? If not, give it a try - that might help you make up your mind
fairly quickly!
Remember Richard Hammond driving those Renault single-seaters on Top Gear?
Thought that this may be of interest. Figures on the left from the progam, those on the right best of three runs, so I think that the figures are a
tad optomistic, either that or I am just slow, :-) Cheers Ray
Power at Flywheel (BHP) : 238
Weight without Driver (KG) : 900
Power to Weight Ratio (BHP Per Ton) : 268.69
0 - 60 (Secs) : 4.39.................................................. 4.54..... 0.15 more
0 - 100 (Secs) : 10.96
60 - 100 (Secs) : 6.57
Drag Strip Quarter Mile (Secs) : 12.66..................... 12.98... 0.32 more
Drag Strip Terminal Speed (MPH) : 109.12
Don't worry I am not taking the handy calculator as gospel as I agree there are other factors to take into account but it is handy to see what
sort of ball park figure I should be expecting. 
here's a video on board a 550kg car fitted with the 1.6 mx5 engine.
Not the quickest machine in a straight line, on this circuit it couldn't break 100mph, just not enough power to beat the wind resistance. The
caterhams in the video had 125+bhp
Click me
If it helps,
I have had a Westfield with 115BHP (it was about 550KGS) and it was pretty darn quick up to about a ton.
I have a 1.8 MX5 with 130 BHP and it is pretty tidy machine (weighs just under a ton)
The 90 BHP engine in the MX5 is a proper weedy unit and is not simply a de-tune, it is a lot shabbier unit than the other 2.
My advice would be the sweet revving 1.6 giving 115 or for a tad more torque go for the 1.8 130bhp unit.
Either way they are great engines, very tuneable and very reliable.
Good luck with it.