How to strap an Elise/Exige to a rolling dyno

[masheen]

i won a dyno session at a silent auction for charity months ago. i went to the dyno facility couple of weeks ago. when they are about to strap the car down by placing steel hooks onto suspension pieces (control arms) i realize i have not thought about that and that i don't feel comfortable with it. so i decided to go home and think about it some and then come back again. there is only a week or two of driving time left here now, and my coupon is only valid this year, so i need to make a decision this week.

(this is a mustang dyno where the rear wheels turn steel cylinders. for a dynapack my question is not applicable as in that case wheels are taken off and the dyno connected directly to rear hubs.)

i have called some people and i have done some searches here and asked in existing posts and got some answers, but i still don't have confidence. so i am about to summarize my current findings here and hope to come to a conclusion.

in this tread How to dyno?, there was first a lot of just what not to do (and that's good to know too), but not a suggestion of how to actually do it, until Post 13 by Simba:

Take the diffuser off, bolt two tow hooks (pegasus, et al) into the front diffuser bolt threads on the subframe with grade 8+ bolts, cross the rear straps over, and you should be good for the rear. Front wheels can just use tie down loops in the wheel spokes, one front, one rear for each front wheel.

the main problem for me there is that i can't picture the part: "bolt two tow hooks (pegasus, et al) into the front diffuser bolt threads on the subframe". does this mean put bolts in those threads and then place hooks around them? if so, i imagine the hooks slipping off. or do these hooks actually usually come with bolt holes? - in which case it makes sense.

another problem is that others have suggested against crossing the straps in the rear due to them being likely to get burned and snapping due to proximity of the exhaust.

have others done it this way?

there is also this approach: Blackwatch XP "FrankenLotus" Build-up i.e. 370HP 1595lb Beastie,
where Post 201 says:

I strapped the front the tow bar in the nose. The rear is suspension arms. I've had no trouble in the hundreds of dyno runs the car has seen. Its not a fragile as you might think.....

here i need to look in the shop manual (will do that today) for the "front tow bar" and then imagine how that will be done.

and there is again suspension arms. the manual specifically says not to use those for strapping the car, but maybe the manual is overly conservative, and it may be that the car does not see as much loading on the dyno (i expect ideally next to none) as it would on a tow truck.

and if many people have done it like this without problems, then i am ok with it. have you?

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Personally I would avoid the suspension arms if you can help it.
Sure they probably would be ok but these can and do bend.

As for the tw hooks methd, that actually sounds very good. He's saying to take he diffuser off and where the two large bolt go that hold the diffuser in place (these are mounted into the rear suspension cross member which is very strong as it's also a jacking point with suitable adapters or four ost lift) screw in suitable hooks and tie down with these. You should be able to find a tow hook that is both strong enough and the correct thread for the bolt holes without any problem.

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Update:
Lotus Elise Maintenance, Oil Change Tutorial

This link shows the jacking points - IIRC the diffuser bolt holes are close to the jacking points labelled "D" in the excert from the manual.

[masheen]

Originally Posted by ads_green

Personally I would avoid the suspension arms if you can help it.
Sure they probably would be ok but these can and do bend.

As for the tw hooks methd, that actually sounds very good. He's saying to take he diffuser off and where the two large bolt go that hold the diffuser in place (these are mounted into the rear suspension cross member which is very strong as it's also a jacking point with suitable adapters or four ost lift) screw in suitable hooks and tie down with these. You should be able to find a tow hook that is both strong enough and the correct thread for the bolt holes without any problem.

it makes more sense now - i didn't read the original tow-hook explanation carefully enough at first - i now see that the idea is to screw tow hooks themselves into bolt holes and then the strap hooks can be attached to them.