4.5 Map Upgrade & Cam Timing

[rjben]

Just had the new TVR Power chip fitted at Fernie’s and it appears to make very little difference. Brian has spoken to both Andy at APM and TVR Power, apparently it should make a significant difference! One possible explanation given by TVR Power is that the cam timing is out. Would I be correct to assume that if the car feels and runs like the majority of other 4.5’s out there, then the cam timing if fine?

Also, does anybody know who can check the cam timing other than TVR Power? Is the timing an absolute figure, or could it be variable according to other tolerances within the engine? Sorry, possibly a stupid question but I don’t have much of a grasp of mechanics.

Any help would be much appreciated. It’s not the cost of the chip that is bugging me. It’s the fact that something is ‘wrong’ with my car and preventing me from extracting its potential.

Cheers,

Rob

[shpub]

Andy at Tower View set mine up the other day. Mine was quite badly out. Hadn't been serviced for some time. The tappets need to be chceked and then he set the timing. Main problem is the lack of timing marks...


>> Edited by shpub on Wednesday 21st July 16:32

[rjben]

Cheers Steve,

I don't suppose you know what the timing should be do you?

[shpub]

Pretty sure that there is no timing figures as you have with distributors and ignition as the cam is setup in relation to the piston movement so that the valves are fully open/closed at the appropriate moment. The cam itself defines what the timing actually is.

[HarryW]

Pretty much as already stated, cam timing is dependant on the cam fitted and knowing TVR this information is probaly not readily available to joe public. It is not to bre confused with ignition timing. Do a search on 'dialing in a cam' it involves fitting external timing wheels to the crank and cam pullies and adjusting the cam pulley wrt to the crank tdc. For instance my 218 cam has a timing of 112 deg btdc (or was if atdc ). A V8D hybrid 218 would be 108 degs etc, this is one area that can be responsible for the big variances between standard engines IMHO. I assume the AJP8 has a vernier cam pulley fitted as standard, only say that as it wasn't standard on RV8 lumps.
I would have thought Andy at APM would have this information, have you spoke to him about it .

Harry

[rjben]

Cheers gents,

Your comments certainly make sense, i.e. timing is not absolute but a function of cam profile related to state of TDC and valve position. When considering this I can't help think that 'all' 4.5's have a 'standard' cam profile as they all have the same basic map. Given this (and no cam wear) it must be possible to have a correct relative offset figure for timing? Sorry, but I really have no knowledge in this area!

I don't want to say anything about my potential fix at the moment as I don't want to spoil my chances with my current line of investigation, but I'll let you know what the outcome is.

Cheers,

Rob

[trooper1212]

Brian at Topcats did the timing on my Cerb a few motnhs back, so you could try giving him a call if you need to.

[rjben]

Cheers Trooper,

I'll give them a call if I can't get to the bottom of this. The fact is is that I don't really think my timing can be out that much as it would probably be running like a dog, I just want to understand why the chip has not had any affect. It's all a bit too complicated for me!

Cheers,

Rob

[gazzab]

take it to Andy at APM and get him to sort!

[beemer]

gazzab said:

take it to Andy at APM and get him to sort!

seconded...

My upgrade chip (from APM) certainly works, if what you're expecting is smoother running throughout the rev range. If you were expecting a nitrous-style increase in power, you may be disappointed.

Does sound like something's not right, mind!

cheers
sean