Adrenaline V Brain

[Longboarder]

My mate Paul has just done destruction testing on his 2.1L pinto engine. He discovered that at 7500 + rpm in fourth his car sounds glorious but not for long. There was a bit of a bang! He got the car towed home and has removed the starter to find the flywheel turns independant of the engine. Not sure if the engine turns. Hope this is just the flywheel bolts that have let go. If its the crank, which was balanced what is the safe limit for a balanced standard bottom end? Is there any way to build a stronger bottom end to take 7500 rpm at reasonable cost? I have suggested an electronic rev limiter as an alternative!

Nigel

[Guest Angel Boy]

He discovered that at 7500 + rpm in fourth his car sounds glorious but not for long. There was a bit of a bang!

Mental note for future:

 

Do not rev past 7500rpm for a long period of time

 

Must have sounded fantastic upto the Bang part though.

 

Hope it doesn't turn out as bad as it sounds.

 

Andy

[Guest Phil Slater]

According to the book I have on tuning the Pinto the standard crank should take 8500 plus. However to ensure reliability up to that point it recommends the fitting of lightweight forged pistons and lightweight aftermarket con rods. The recommendation for a standard flywheel when lightened and perfectly balanced is that it's satisfactory upto 7500 rpm but with "at least" one dowel fitted. Also, that for safety sake any engine that is turning more than 7000rpm on a regular basis should be fitted with a lighweight steel flywheel assembly.

 

Don't know if this helps - but that's what the book says.

 

Phil Slater

[Longboarder]

Paul has stripped down the engine and its the flywheel bolts that have sheared. Taken the crank and flywheel into the machine shop to be tidied up, checked and dowelled. He is also buying a rev limiter but is looking at a device that allows full throttle gear changes as well. He doesn't want launch control because he wouldn't be able to smoke the tyres!

 

The right foot is mightier than the brain!

 

Nigel

[Guest Simon cooper]

Quite an interesting read this one. 7,500 revs in forth? was it going down hill?

You or your mate will not be able to fit full power shift to a Sierra box.

A. It needs to be a sequential box

B. Poor old Mk 9 will not take it.

C. Syncro's would not work

Launch control does not stop the wheels smoking. You set it to where you want. if you use it properly it will knock at least 1.5 secs off your 0-60. For it to stop smoking tyres it would bog down so low that you would not move.

Sorry to dampen your enthusiasm.

Simon

[Longboarder]

Pity about the full power gear shifts. When I spoke to Paul today he was mostly relieved that he hadn't totaled his bottom end. He does say he was doing 125 on the flat at the time it all went pear shaped. (I don't know what final drive he has fitted.) His was chasing a friend who has a stripped out Westie with a beautiful 1700 crossflow in it. Paul's engine was dyno'd at 140 at the wheels and he wasn't catching Magic's Westie. Allowing for a little exageration he was still going some. Last ride I had with him the rev counter was bouncing of the stop and I adopted a foetal position, 1. To get my feet out of the way of the expected engine explosion. 2. I was terrified!

Plain soft cut rev limiter seems like the sensible option, set to about 3000 to slow him down a bit!

 

Nigel