11 replies to this topic

[timothy]

I am currently brainstorming my ideas for what to do about an engine build. I want something that is going to be quick, around 100bhp, but useable on thye motorway as I'm at uni and do quite a few motorway miles visiting mates.

My first idea was to drop the 1.3 16v engine from a suzuki swift in. However I'm thinking of getting involved in hillclimbing and to compete in the modified production car class, the car needs to reatin the original block.

I then had an idea to build a fast road spec 1380, and to use a lower final drive ratio of 3.211 instead of the standard 3.444 to make it more motorway friendly as this would give me a theoretical 73 mph at 4000rpm and 92 at 5000 instead of 68 and 85.

Will changing the final drive really make the car more motorway friendly? How badly will it affect acceleration going from 3.444 to 3.211? And finally will the car be much slower with the 1380 built to around 110 bhp, as oppossed to fitting the swift engine which has about the same, but is all alloy and presumably more efficient at transfering the power from the flywheel to the wheels?

cheers

Edited by timothy, 29 October 2006 - 10:34 PM.

[biggav]

I have a 1380 stage 4 which must be monkeying around the 110 bhp mark.. currently on a 3.44:1 cwp set up.. i have managed to buy a 2.76:1 from someone on here and will be fitting it as soon as it arrives.. i will let you know the outcome. I was a bit worried about the loss of acceleration so i also have a nice big bottle of nitrous oxide which will be going on too!!!

[timothy]

yeh that will be interesting to see how it affects it. is it a screamer on the motorway now? how quick is it with the 3.444, rough 0/60 or 1/4mile times? I'm hoping 3.211 is low enough to make it comfortable because I don't want to sacrifice too much acceleration

[biggav]

Guessworks is the Forum Gearbox Wizard. click the link...

GUESSWORKS MAGIC PAGE

The calculator will tell you what speed you will be doing at what rpm dependant on wheel size, final drive ratio and gearbox type... its really is rather good.

[fikus01]

im not sure it will destroy the performance but you'll definately be able to hang on to those gears for longer!! the twin points do a good 40 in first!! 70 in second!!, u get the picture!! (this is at 6500rpm aka the limiter)

[timothy]

I had a look at guessworks' page, it was very useful, cheers.

40 in first and 70 in second is a bit too low, that must be around 2.7:1.

Does anyone on here run a 3.211:1 fd with a standard box?

[Guess-Works.com]

to be honest, you'll not notice much difference between the 3.4 and the 3.2, just a bit extra length in the gears, an extra 300 rpm at motorway speeds...

If you realy want a motorway cruiser then you realy need to drop into the 2.9's to get anything noticable..

As for hilclimbing, the norm is to go for a short diff, 3.7 and upwards, and that and motorway driving is just not compatable.

[timothy]

if i were to drop it down to the 2.9's, how badly would this affect the acceleration?

[biggav]

Its hard to say as every engine is slightly different... The last run of mini's (post 1996) ran 2.76:1 and they still accelerated quite well.

The thing is, you are trying to build a hill climbing motorway muncher which is kind of hard to do. As GW says, hillclimbers have great acceleration and low top end.

If you have the funds, you could use a 5 speed box and a 2.9 diff... the first 4 gears being close ratio and the 5th being 1:1 for motorway use????? or a 4 speed with 4 being 1:1 and the other three being lower ratio to give better acceleration...Not being a gearbox man i may be talking rhubarb though....

[fikus01]

the twinpoints i've driven are more like 3 speed gearboxed with an overdrive!! 4th really doesnt perform anything except cruising!!

[blacktulip]

i agree with every engine is different, top end driving can depend on the cam too. my girlfriend has a tuned 1275 and its alot better top end driving than my 998 with the same diff. so it all depends on the set up. i once had a 1330 with a 3.7 and it was dreadfull on the b roads let alone the motorway. personally i would/am go/going for a 3.2. see how u get on mate!

[timothy]

cheers for the replys, I'm hoping that it all falls together ok. Need to start planning my engine rebuild now...hmmm 1330 or 1380. Indecision is a *Female doggy*