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Motor Math Calculations and Pinto Engine
VinceGledhill - 12/9/03 at 08:44 AM

I've just been looking at my calculations for the items that I plan to install into my car.

I have just purchased a capri live axle from "Zippy" (Metal Hippy) on here and the calculations run as follows.

Running a ford type 9 gearbox from my donor car and the capri back axle I get the following at 6000 revs

1st 31mph
2nd 57mph
3rd 82mph
4th 112 mph
5th 136 mph.

I was hoping to get to the 60 mark in second gear. In order to do this I will need to rev the engine to 6500 RPM. Will it take this sort of speed? What modifications will I have to make if I do?

Or should I change the ratio of the diff? Another diff from a 2.0 instead. With the different ratio of the 2.0 which "Mark" thinks is 3.54/1 I would get the following

1st 32 mph
2nd 60 mph
3rd 86 mph
4th 118 mph
5th 144 mph

Thoughts? Please don't say get a bike engine...... or some such..... maybe in the future but not pre SVA or the first year or two that it is on the road.

stephen_gusterson - 12/9/03 at 08:52 AM

the yahoo list (TOL)

http://groups.yahoo.om/group/locost

has a spreadsheet in the files area that will work out all that stuff for you.

whats magic about 60mph btw?

atb

steve

VinceGledhill - 12/9/03 at 08:58 AM

I've got a program called motor maths that has done the calculating. My questions were.....

Will a pinto take 6500 RPM?

If not what mods do I need to make so that it will?

Or would I be better off changing the diff?

60 is the top figure in a 0-60 time. I would like to get there in second gear.

David Jenkins - 12/9/03 at 09:39 AM

You could always try fitting a set of Quaife gears in your gearbox - they raise the 1st gear from a too-low 25mph max to around 45mph max, so I guess that the rest of the gears will be higher as well.

A new set is expensive, but I have seen them for sale 2nd-hand.

David

timf - 12/9/03 at 09:42 AM

to take 6500 rpm reliably you realy need steel crank and rods (V expensive) the cossie stuff will fit with machining but again expensive if your only going to do it occasionally then a fully balenced / lightened bottom end will manage but make sure all the rods are pollished to stress relive them and the crank is ground with generous radi on the journals

Peteff - 12/9/03 at 09:55 AM

I have a Capri 2.0 axle in mine and according to the diff tag it's a 3:44.1. If you use different size rear wheels and tyres to original you will be altering your gearing and might look into that as a way of reaching 60 in 2nd if you really need to.
You will have to do some juggling to get the speedo right unless you are going electronic.

yours, Pete.

VinceGledhill - 14/9/03 at 07:09 PM

Thanks Guys. I'll probably be going electronic with the speedo. It's such a simple and effective solution.

Mark Allanson - 14/9/03 at 07:42 PM

"to take 6500 rpm reliably you realy need steel crank and rods (V expensive)"

I have a 205 block. I am lead to believe that this is a cosworth bottom end, what is the safe rev limit for this engine?

Stu16v - 14/9/03 at 11:58 PM

quote:

I have a 205 block. I am lead to believe that this is a cosworth bottom end, what is the safe rev limit for this engine?


It isnt a Cosworth bottom end Mark. 205 signifys a block that was originally designed for the Transit, but in beefing up the block for reliabilty, Ford made it suitable for turbocharging application (and 16 valves). Cozzy block sounds better than Tranny block..... However, everything else in the engine is different depending on application...

Vince, why do you want to reach 60 in second? I guess it is to try and reduce the 0-60 time....

[Edited on 15/9/03 by Stu16v]

gjn200 - 15/9/03 at 07:23 AM

Why not use bigger tyres?????????????????????

VinceGledhill - 15/9/03 at 07:26 AM

Yeah to reduce the 0-60 times. If you have another gear to shift up there's "got to be" a time loss. Especially when the gear you are going 2nd to 3rd. Not a quick gearchange that one.

I've actually decided that I am going to fit the 1.6 capri back axle that I've got. It's not a major job to change it again afterwards. A job I could do in a day if I had to.

I will more than likely be going the electronic speedo route so that isn't going to give me any problems.

VinceGledhill - 15/9/03 at 08:56 AM

Can I get bigger tyres in the rear arches?????

david walker - 15/9/03 at 09:43 PM

quote:
Originally posted by timf
to take 6500 rpm reliably you realy need steel crank and rods (V expensive) the cossie stuff will fit with machining but again expensive if your only going to do it occasionally then a fully balenced / lightened bottom end will manage but make sure all the rods are pollished to stress relive them and the crank is ground with generous radi on the journals



Not true. Cast crank is happy to 8000 when balanced. Cossie cranks aren't so good in n/a applications. Corners are undercut on cast crank so you don't grind a radius in them! "Injection rods" from a 205 motor are happy to 7000+.

Stu16v - 15/9/03 at 11:08 PM

quote:

Yeah to reduce the 0-60 times. If you have another gear to shift up there's "got to be" a time loss. Especially when the gear you are going 2nd to 3rd. Not a quick gearchange that one.


Very true mate. But dont get *too* hung up on reducing the 0-60 time, because in reality, it's a load of bollox (IMO), that doesnt prove anything.
As a rough example, two cars leave the line on the drag strip. Car 'A' got to 60 mph quicker, yet car 'B' crossed the line first. Taking the differences of driver reaction/ability out of the equation, car 'B' won because the ultimate measure of speed is who gets to the finish first, and not how fast the car is to a certain speed. How often do any of us race to 60 mph?
Unfortunately acceleration is not accurately measured by a 0-60 time, it is only a rough indication of how fast a car is from a standing start.

FWIW, my car has a 16v Vauxhall motor in it, and I think that with my present gearing, if I bounced it on the rev limiter I could just scrape 60 in second. But I dont, because it's beneficial to get it into third before the engine runs out of breath-and I'm not stopping at 60...

[Edited on 15/9/03 by Stu16v]