Torque mount warning for higher power 1.5's

[Paul Woods]

Please read this chaps,something new in the 1.5 world has come to our attention.Stu contacted me to show me pics of his chassis area where the front and rear torque mounts attach,and one of the captive nut areas in the chassis have fractured and broken away.He spotted this while changing the clutch.Its the first time we have ever seen this on any 1.5,and i mean worldwide!!!





And the rear chassis has a slight crack forming around the captive nut...



Now before everyone starts panicking dont worry,this car is driven to the very limit on the drag strip and on track so penelope really gets some serious hammer time! the torque mounts are taking the full brunt of those hard launches.Also this car is running at a lot higher torque level than most,that too is a contributing factor.What we dont quite understand is why no other 1.5 in the world has shown this fault up to now? There are some pretty high power 1.5's out there and none of them have done this....so its a bit confusing.Niks rev3 is running 290bhp and has no signs of this at all.

Both stu and i though it was in everyones best interests to make this known as its something completely new in the 1.5 world.

Regular 1.5's running normal power need not worry about this at all,i ran mine for years with no problems at all,as have many other owners throughout the world.

This warning needs to go out to anyone thinking of running plus 280bhp and competing in motorsport events.

The solution is very simple indeed,all we need to do is weld some 3mm plate over these areas to beef them up a little,probably take an hour or two maximum.Certainly theres no design flaw with the torque mounts or anything,it seems in penelopes case the front torque mount rear bolt was taking too much load under hard launches...so we need to spread that load with thicker wider plating in these areas.

Many thanks to stu for bringing this one to our attention,his car is certainly maxing out 1.5 testing for all of us :thumbsup:

[wangan_x]

couldn't just be that its a UK and therefore rust ridden model?

[Stu]

No rust on this car mate:thumbsup:

[GaryA]

couldn't just be that its a UK and therefore rust ridden model?

Or maybe Santa Pod and a little drive around the Eifel mountains had something to do with it .

[Paul Woods]

personally i think its a combination of extremely hard launches and the amount of torque this engine is producing,only one area has failed after a year of solid abuse and thats the rear bolt on the front torque mount....so we will need to start beefing these up which will take about 20 minutes during the conversions.

[Zip]

personally i think its a combination of extremely hard launches and the amount of torque this engine is producing,only one area has failed after a year of solid abuse and thats the rear bolt on the front torque mount....so we will need to start beefing these up which will take about 20 minutes during the conversions.

Torque did this you say?

Whats going to happen when the V6s start to get tuned up high

[Paul Woods]

lol they'll rip the bulkhead off lol

seriously though this is one captive nut on an extended piece of chassis that looks pretty weak,obviously its up to 4a-ge spec but with a combination of high torque and very hard launches over a long period of time its caused a stress fracture.

Im just grateful to stu for telling us about this,its something new that has only happened cos stu really gives his car a good thrashing at motorsport events.

[Jiff Lemon]

Stu, did you fill fill your torque mounts? Just wondering if excess movement in the rubber is then being passed through to the mount?

[MartG]

May be worth considering drilling a hole in the top of the chassis member, and using a long bolt which can engage in both the captive nut and have a nut tightened on the top surface too IYSWIM

[Driftin_AW]

hey dudes, there is actually a reasonable amount of info about this on the US board. I actually got into a debate with a guy about what exactly causes it. It's clearly a fatigue failure, and as such isn't just due to one or two very high stress moments, but rather an accumulation over time. A lot of guys with lowly 4ages have had this happen to them also.

Due to the direction that the engine twists, the pulling out failure on the front torque mount is actually due to engine over-run (decelerating with car in gear). This makes me think that power/torque doesn't play a huge role in this failure, but rather it's to do with how it's driven. I'm thinking the major cause would be if you're revving quite high and let your foot off the gas without popping the clutch in. The engine will suddenly try to not rev (effectively acting like a brake), while the momentum of the car forces the engine to continue revving. This makes the engine rotate forwards (basically the intake manifold moves forward, sump moves backward) and loads up the captive nut on the front torque mount profusely! Since the effectiveness of an engine to provide engine braking, and so the load on the front torque mount when in overrun/engine braking situations, is not effected by it's power output; rather a combination of things like compression ratio, engine size etc, it really shouldn't make too much difference how much power you're putting down.

Anyway my thoughts on the best way to fix/prevent this is to put a thick plate on the top side of that sticky-outy-bit (to spread the load better), drill right through the captive nut, up through the top of that sticky-outy-bit and the plate you've attached to the top, large enough to put a bit of tube in to prevent it crushing, put tube in, then through-bolt the whole thing.

[note, just read above and saw MartG has a similar suggestion - good one :) ]

Oh and as a final note, filling your torque mounts with urethane is likely to make this worse because it will transmit more vibration. I'd imagine good condition standard rubber is probably the best for absorbing the forces and spreading them over time to reduce the likelihood of this happening again