CoG - effect of raising an engine in the chassis

[TorAtle]

The front of the K-series engine looks like it is lower to the ground that the gearbox side. It also looks like it would be relatively simple to raise it by using spacers under the engine mounts (obviously there'll be some clearance issues to deal with).

 

For a 500kg car, let's assume engine and gearbox is 120kg and rim/tyres/suspension is 80kg. So for every millimetre 120kg is raised, you could lower 300kg by the same amount. The numbers aren't a 100% correct, but a 3:1 ratio isn't too far off.

 

There's not much in the archives about this, but clearly the CoG would be lower, so why aren't we doing this?

 

 

[shn7]

Could it be to do with making sure that the propshaft doesn't run absolutely straight as it needs some angle on the joints . I could well be speaking out of my 🙆🏻 at this point.

 

Steve.

[Jason Plato]

Tor , I agree in principle . I think you could raise the K engine 15mm if you could overcome the dry sump pump hitting the steering rod , and the bellhousing hitting the foot well ( you may get away with this one?).

 

But then when you lower the chassis , the suspension will not be at its optimum angles on the wishbones and you could have a lot of bump steer . .?

 

Maybe if you fitted wider wishbones the bump steer could be reduced ??

 

 

[Chelspeed]

You can shim the rack up to get the bumpsteer better.

[TorAtle]

Steve, there's a flexible joint (lack of correct term) between gearbox and diff, so this shouldn't be an issue.

 

Dave, I think it's possible to dial out the bump steer by shimming the steering rack. As for the camber, by lowering the car the static part of the camber will be greater than before compared to the dynamic one. So even though you can set the camber to whatever value you wish (stationary), the camber change caused by wheel movement will be less than before. Or so I think!! Don't know if this is a plus or not.

 

So is it worth thinking about? It would be an ideal time for me to try it out now...engine bay only contains engine (more or less) and I'm waiting for parts, so...idle hands looking for work.

[Jason Plato]

Yes , lets investigate .....

 

I'll get some more accuarate measurements on the clearance between the bonnet / nose cone and engine . And check if anything else could clash ....

 

I'll report back tomorrow .

 

Dave

[TorAtle]

I've already had a short look. The clearance between crossmember and primary #4 is pretty marginal. For me the steering column and alternator is a concern, you have the dry sump pump to worry about. Top of engine is not a problem with a K16 casting, if it is with a VVC or VHPD head then a Julian Thompson cam cover should sort it. As you say the bellhousing is close to the footwell but I think it will be ok.

 

Looks doable.

[shn7]

Tor,

 

I know there's a universal joint at each end of the propshaft but that's was my point. I don't think, from what I've read elsewhere, these are designed to run in a perfectly straight line.

 

Steve.

[Normans_Ghost]

UJ's should run OK in a straight line, or any small angle (not too much)

 

Norman Verona, 1989 BDR 220bhp, Mem No 2166, the full story here

[shn7]

Norman,

 

That's interesting to hear. I've read on a couple of other kit car forums advice to people to make sure there is a small angle as running them true is not good for the joint. Something to do with not exercising (flexing) the joint .

 

Steve.

[TorAtle]

Dave, any further thoughts on the matter?

[SLR No.77]

Steve, during use the straight line will be flexed anyway due to the up and down movement of the rear suspension

 

Stu.

[shn7]

Stu,

 

Only if it's a live axle. Not true for De Dion.

 

Steve.

[SLR No.77]

Aahhh - DeDion

[Bare]

All vehilces with a propshaft have a designed in offset.. something to do with harmonics .. regardless, it's a universal setup, apparently with time proven reason.

Lotsa info available..IF.. one wants to adequately research.

[TorAtle]

According to Simon Lambert, "The only problem with raising the engine is clearance between the engine and the bonnet. "

 

Neat. I'll hang on to that mail in case something brakes

[thinfourth]

hang on basically what you are saying is that raising the engine lowers the CoG

 

Okay lets take this to a logical progression If i mount my engine ontop on my bonnet will the COG be lower or higher.

 

 

 

Sod the heater wheres my shades

[Chelspeed]

> hang on basically what you are saying is that raising the engine lowers the CoG

 

Of course he isn't give the man some credit! He's saying there's a minimum ground clearance under the sump that you can get away with on the road. If you raise the engine in the chassis you can lower the whole car to get back to the same minimum ground clearance. As the rest of the car is heavier than the engine this will have the effect of lowering the CofG.

[thinfourth]

Okay i misread the post

 

Now that does make sense lowering the car while keeping engine at same height.

 

Sod the heater wheres my shades

[TorAtle]

Glad that misunderstanding is sorted

 

I've now raised the engine by 6mm using an alloy plate under each engine mount. This is about the limit if you have a SLR 4-2-1 exhaust, the diagonal brace is now pretty close to primary #4. The engine is more level, and I would guess another cm will be needed to get it completely horizontal. There are other clearance issues as well, but since mine is a LHD I won't go into detail.

 

I'll raise the engine further when I get hold of a thicker aluminium bar.

 

 

[Jason Plato]

The K engine can be raised 20mm - any more and the cam cover sits too close to the nose cone/ bonnet, but it does depend on the clearance you have aroudn the manifold and x member as you say Tor .

 

I'm waiting for my new manifold before I raise mine . The new manifold will be shaped based upon the modified engine position

[EFA]

Nice to see you guys are getting up to date. Raised the engine in my car about 4 years ago.

[Jason Plato]

😬

 

But we are doing it intentionally

[Mike Bees]

Your front suspension geometry will go to pot if you lower the chassis too far. I know from running 205x50/15 tyres on the front that if you have too much dihedral on the front wishbones then the steering becomes quite nasty and I believe excessive amounts of camber change. Best to keep them bottom wishbones more or less parallel with the road.

 

Mike

 

Edited by - Mike Bees on 28 Apr 2005 16:31:33

[NoLimits]

I have 19mm (it was a standard size apparantly) square bar spacers under my mountings.

 

I did this last august after wiping out a dry sump on a cats eye.

 

As DJ has said its not the conning tower that actually hits the bonet first its the Cam Belt cover.

 

I had to alter the panels around the exhaust primaries.

 

Things to note as I also had a set made for OAP were that although only seperated by one chassis number (both SLRs) the diagonals were in slightly different positions. His primaries came closer to the diagonal than my own.

 

Steering column was close but not a problem.

 

As sugested I then lowered the car back down. (A bit) 😬

 

However the main reason as far as I was concerned was to allow me to run at optimum chassis levels whilst increasing ground clearance.

 

This definately worked as the old sump was unreadable

 

The new sump was clean as a whistle untill LONGCROSS 😳

 

DJ will explain I'm sure.

 

Anyway car handles fine.

 

I have a pattern available or I can have them made for £5 / set plus postage.

 

 

 

MY 51VEN

Give it some Welly