Solid Engine Mounts
Discussion
I am about to fit a new engine/gearbox into my Dax Rush (Honda S2000 engine and gearbox btw) and after juggling with it in situe have found that the standard engine mounts will push it too high so I am considering going along the route of fabricating solid mounts and bolting it straight to the chasis. However before I commit to this I was hoping there might be others around who own cars or have built cars with the engine mounted solidly who could advise me whether this is a wise thing to do. (excluding motorcycle engined cars as these engines are normally designed to be mounted straight into the chasis)
I know Caterham have their CSR which I believe has the Duratec lump mounted straight onto the chasis.
Things I am concerned about are - are the engine and gearbox pick up points strong enough for the job? is vibration a problem (considering i'm using a bog standard Vtec engine I can't imagine it will be too lumpy) Will the torque stresses now be focused on the Diff?
I know Caterham have their CSR which I believe has the Duratec lump mounted straight onto the chasis.
Things I am concerned about are - are the engine and gearbox pick up points strong enough for the job? is vibration a problem (considering i'm using a bog standard Vtec engine I can't imagine it will be too lumpy) Will the torque stresses now be focused on the Diff?
Solid Engine Mounts - not a good idea in my mind - you will lose all your fillings, rattle things of the engine, and get sick of the noise of resonating floor panels and side panels. I have been in a 1430cc rally / grass track mini with solid mounted engine, and even when mounted into a subframe with nylon mounts between bidy and subframe the din / vibration was terrible...
The best option is to angle grind off the original "Plate metal" engine mounts (without scarring or cutting into the chassis tubes at all) , and then make up replica mounts and weld them on lower in the engine bay, and ggo for the standard Honda S2000 engine mounts as Honda engineers will have spent mega bucks designing and testing mounts which give the car a low amount of engine vibration feedback, and allow for the "take up" of clutch / transmission being engaged to allow the engine to lean over during this process : makes the car smoother / more controllable when drive is engaged (assuming it is not an auto box of course). If this doesn't appear possible due to geometry of chassis tubes, you could junk the honda metal bracket between rubber mouunt and the engine and fabricate a new one of those from sheet metal , but of a design that means its higher up the engine block.
Failing that talk to DJ Sportscars - they will make up mounts for practically any engine to be fitted in to the Rush model, and if you change engine type they can perform mods or provide verbal advice.
The best option is to angle grind off the original "Plate metal" engine mounts (without scarring or cutting into the chassis tubes at all) , and then make up replica mounts and weld them on lower in the engine bay, and ggo for the standard Honda S2000 engine mounts as Honda engineers will have spent mega bucks designing and testing mounts which give the car a low amount of engine vibration feedback, and allow for the "take up" of clutch / transmission being engaged to allow the engine to lean over during this process : makes the car smoother / more controllable when drive is engaged (assuming it is not an auto box of course). If this doesn't appear possible due to geometry of chassis tubes, you could junk the honda metal bracket between rubber mouunt and the engine and fabricate a new one of those from sheet metal , but of a design that means its higher up the engine block.
Failing that talk to DJ Sportscars - they will make up mounts for practically any engine to be fitted in to the Rush model, and if you change engine type they can perform mods or provide verbal advice.
Dax hard mount the bike engines in the Rush, mine has a nice, solid cradle to hold the engine, no insulation at all.
There is some vibration but not enough to be uncomfortable. I you're looking for a comfy car for Sunday runs with the Mrs then you might prefer insulated mounts but I'm perfectly happy with mine. (Is the S2000 engine more vibey than a Hayabusa ??)
You do need to be careful if you don't have insulation, for example the vibration broke the bracket that came with my fuel pressure regulator - it was rivetted to the engine cradle so got the full vibration. If the chassis isn't designed to cope with this then you might have problems. (Rush bike chassis is obviously, not sure about car chassis)
There is some vibration but not enough to be uncomfortable. I you're looking for a comfy car for Sunday runs with the Mrs then you might prefer insulated mounts but I'm perfectly happy with mine. (Is the S2000 engine more vibey than a Hayabusa ??)
You do need to be careful if you don't have insulation, for example the vibration broke the bracket that came with my fuel pressure regulator - it was rivetted to the engine cradle so got the full vibration. If the chassis isn't designed to cope with this then you might have problems. (Rush bike chassis is obviously, not sure about car chassis)
Agree with Steve D : Dax do a neat job of welding / braketing the chassis (would be a shame, as well as difficult to move the mounting points) , my second suggestion of fabricating a bespoke pair of engine to rubber mount engine brackets (using same pick up points on the engine which will have been designed to take the stress / torsional loads) is probably favourite. Engine to rubber mount brackets usually are bent / welded plate steel or plate and square steel tube welded combinations, thus easy for a local engineer or welder to make up so long as they have measurements and drawings or prefferably cardboard or wood mock ups to work from. Should be inexpensive too.
As for BEC Busa Rush - I've been in facory demo car and agree Vibes are not bad and exhaust sounds wicked so you can't hear transmitted whines / clatters (I think my 4.6ltr V8 rush vibes more !!).... The Bike Engine is much lower moving mass : tiddly little crank , con rods & pistons compared to a car engine because torque is less of a requirment on bike engines, they are balanced to many times higher tolerance tahn car motors due to the high revs they achieve, and thus they always vibrate less than car engines.
Perhaps the full answer is that Car Engines need rubbers and BECs if well designed don't.
As for BEC Busa Rush - I've been in facory demo car and agree Vibes are not bad and exhaust sounds wicked so you can't hear transmitted whines / clatters (I think my 4.6ltr V8 rush vibes more !!).... The Bike Engine is much lower moving mass : tiddly little crank , con rods & pistons compared to a car engine because torque is less of a requirment on bike engines, they are balanced to many times higher tolerance tahn car motors due to the high revs they achieve, and thus they always vibrate less than car engines.
Perhaps the full answer is that Car Engines need rubbers and BECs if well designed don't.
If it helps at all.....
..had an old Lancia TC in my car and suffered shocking vibrations. This was with rubber mounts. Stripped engine, had it balanced, SLIGHT improvement. Tried softer mounts, bit better, took TC out and fitted an Alfa V6. Vibration gone.
So....it makes a huge difference which engine you are using all other things being equal. As you say, a VTEC should be pretty smooth. But even so, I think I'd still like some rubber in the joint.
Have you thought about using Spax bushes for the mounts?? BB18 type would work well.
HTH
..had an old Lancia TC in my car and suffered shocking vibrations. This was with rubber mounts. Stripped engine, had it balanced, SLIGHT improvement. Tried softer mounts, bit better, took TC out and fitted an Alfa V6. Vibration gone.
So....it makes a huge difference which engine you are using all other things being equal. As you say, a VTEC should be pretty smooth. But even so, I think I'd still like some rubber in the joint.
Have you thought about using Spax bushes for the mounts?? BB18 type would work well.
HTH
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