4.2s that are actually 4.5s inside, cam timing & ECUs
Discussion
Partly for the benefit of anyone not of Facebook, but also because I didn't get an answer about the maps - I'm hoping Joolz will see this!
When I pulled the 4.2 out of the crashed green Cerb I was interested to see it had the same purple dip stick our 97 4.5 (or GT) has:
So I posted some pics on FB, Mr Melling replied confirming that the 45 stamped into the back of the heads shows if your 4.2 is actually a 4.5
According to him the post 99 AJP Cerbs all have the same maps:
Seems a bit odd as it still has the 4.2 inlets & the different exhaust....
I thought I remembered hearing somewhere the cam time was different on them too, but Mr Melling said there was only one setting for all AJPs - even at TDC.
I found mine was set with the exhaust about 6mm lower on both banks:
On the even side the only way to get it back to even at TDC is to jump a tooth on the cam sprocket, not impossible but it seems like some one when to a lot of trouble to set it up like that rather than it being a mistake...?
The main thing I'm wondering is what the cam timing was when that factory map was written?
You have Al saying it should be even (it that to say it should have always been?) Certainly it was talked about as being the norm on here for many years too, but obviously we have the factory literature saying 1.5mm lower....
When I pulled the 4.2 out of the crashed green Cerb I was interested to see it had the same purple dip stick our 97 4.5 (or GT) has:
So I posted some pics on FB, Mr Melling replied confirming that the 45 stamped into the back of the heads shows if your 4.2 is actually a 4.5
According to him the post 99 AJP Cerbs all have the same maps:
Seems a bit odd as it still has the 4.2 inlets & the different exhaust....
I thought I remembered hearing somewhere the cam time was different on them too, but Mr Melling said there was only one setting for all AJPs - even at TDC.
I found mine was set with the exhaust about 6mm lower on both banks:
On the even side the only way to get it back to even at TDC is to jump a tooth on the cam sprocket, not impossible but it seems like some one when to a lot of trouble to set it up like that rather than it being a mistake...?
The main thing I'm wondering is what the cam timing was when that factory map was written?
You have Al saying it should be even (it that to say it should have always been?) Certainly it was talked about as being the norm on here for many years too, but obviously we have the factory literature saying 1.5mm lower....
Mines the same, I believe: I think the story goes that the 4.2 blocks were needed for the Tuscan challenge cars, so the 4.5s were used on some of the customer cars instead, using the 4.2 inlets etc. Not all the customers may have appreciated that... I'm also lead to believe the 4.5 bottom end, with 4.2 inlets is a bit of a sweet spot, but that may just be internet waffle.
MarkwG said:
Mines the same, I believe: I think the story goes that the 4.2 blocks were needed for the Tuscan challenge cars, so the 4.5s were used on some of the customer cars instead, using the 4.2 inlets etc. Not all the customers may have appreciated that... I'm also lead to believe the 4.5 bottom end, with 4.2 inlets is a bit of a sweet spot, but that may just be internet waffle.
The race blocks and road blocks are different .. race blocks have 2 ears at the front for the oil / water pumps and scavenge pumps, the road blocks only have one ear on the driver side for the oil and water (and pas off the back) pumps.As far as I know (and we were working on cerbs before general release to the public) .. there never was a cam timing for customer cars of equal lift on overlap, it was always that 1.5mm method that is described in the ajp build manual.
I'm also not aware of any changes to the timing for the RR version either, but i set all my cars to equal lift anyway because 1)it's good for power and 2) you don't need any special tools to set it up that way. also 3) close enough is close enough, you don't have to be to within 0.5degrees .. if you're +/- 2 degrees out I doubt you'd tell any difference unless you're on a state of the art engine dyno measuring 0.5hp change on a 400hp engine!
I'm also not aware of any changes to the timing for the RR version either, but i set all my cars to equal lift anyway because 1)it's good for power and 2) you don't need any special tools to set it up that way. also 3) close enough is close enough, you don't have to be to within 0.5degrees .. if you're +/- 2 degrees out I doubt you'd tell any difference unless you're on a state of the art engine dyno measuring 0.5hp change on a 400hp engine!
spitfire4v8 said:
As far as I know (and we were working on cerbs before general release to the public) .. there never was a cam timing for customer cars of equal lift on overlap, it was always that 1.5mm method that is described in the ajp build manual.
I'm also not aware of any changes to the timing for the RR version either, but i set all my cars to equal lift anyway because 1)it's good for power and 2) you don't need any special tools to set it up that way. also 3) close enough is close enough, you don't have to be to within 0.5degrees .. if you're +/- 2 degrees out I doubt you'd tell any difference unless you're on a state of the art engine dyno measuring 0.5hp change on a 400hp engine!
Thanks Joolz, Al has some interesting points of view, I wonder how much involvement he had with the actual production cars.I'm also not aware of any changes to the timing for the RR version either, but i set all my cars to equal lift anyway because 1)it's good for power and 2) you don't need any special tools to set it up that way. also 3) close enough is close enough, you don't have to be to within 0.5degrees .. if you're +/- 2 degrees out I doubt you'd tell any difference unless you're on a state of the art engine dyno measuring 0.5hp change on a 400hp engine!
I thought I remembered Dom telling me the RR cars had higher compression from a skimmed head, not different cam timing too.
Most of the things Al says revolve round the AJP he designed with it’s original cams that couldn’t pass an emissions test & the tulip valves he often talks about. It very interesting to hear about that & he obviously did a brilliant job of designing an amazing engine we all love, but he is often caught out on the details of the production cars. He didn’t know anything about the exhaust manifolds being far too small on the production engines. I posted some pictures of mine to try to illustrate, he somehow missed the point & had a go at me for messing up his design!
Luckily someone else stepped in & confirmed the size of the manifolds, Al was shocked….
keynsham said:
So, are these 4.2 litre engines actually 4.5 litre engines? Am I missing something?
Basically yes! It was quite well known on here years ago that all the late model AJP cars were actually 4.5 litre. Apparently as Cerb production went on TVR found it was more cost effective to just have one set of engine internals.
We just didn’t know the date that happened, we were assuming it was a lot later than 99. I still don’t know for sure if it was all AJPs from 99 on….
Of course I’m only taking Al’s word that this is a 4.5 inside, I think the only way to tell for sure would be to take the heads off. A good few people have done that & found their 4.2 was actually a 4.5.
There is probably a bit more to it that that as we had a good few rolling road shootouts on here back in the day. From memory the cars sold as 4.5s made more power than the 4.2s, some quite a bit more. The 4.2s were generally more consistent in power output. (If someone was bored it would be interesting to look at the results from some of those days & see what year the 4.2 were.)
Probably the most interesting question now is how many BHP Joolz can get out of these 4.5s that have the 4.2 inlets & exhausts!
Byker28i said:
A friend had one, I sent him to Jollz - about 380bhp but driveability is much improved.
Interesting, from memory the 4.2 on the shoot out days used to make about 340bhp so still probably a decent improvement. Driveability is more important really though, you notice that more these days will modern cars being so much better than they were 20 years ago…spitfire4v8 said:
As far as I know (and we were working on cerbs before general release to the public) .. there never was a cam timing for customer cars of equal lift on overlap, it was always that 1.5mm method that is described in the ajp build manual.
I'm also not aware of any changes to the timing for the RR version either, but i set all my cars to equal lift anyway because 1)it's good for power and 2) you don't need any special tools to set it up that way. also 3) close enough is close enough, you don't have to be to within 0.5degrees .. if you're +/- 2 degrees out I doubt you'd tell any difference unless you're on a state of the art engine dyno measuring 0.5hp change on a 400hp engine!
You're in to Torque Flanges to achieve those sort of tolerances and they're £10k a pop. They'll give you 0.25 Nm on a dyno that would do 400hp.I'm also not aware of any changes to the timing for the RR version either, but i set all my cars to equal lift anyway because 1)it's good for power and 2) you don't need any special tools to set it up that way. also 3) close enough is close enough, you don't have to be to within 0.5degrees .. if you're +/- 2 degrees out I doubt you'd tell any difference unless you're on a state of the art engine dyno measuring 0.5hp change on a 400hp engine!
Most Eddy Current Load cells that people use (if they're even calibrated correctly, correction for local gravity anyone?) are likely to have an accuracy of 0.25% of Full Scale Torque. For that range, you're looking at 4 Nm.
Byker28i said:
Luckyone said:
Probably the most interesting question now is how many BHP Joolz can get out of these 4.5s that have the 4.2 inlets & exhausts!
A friend had one, I sent him to Jollz - about 380bhp but driveability is much improved.GP
Luckyone said:
Byker28i said:
A friend had one, I sent him to Jollz - about 380bhp but driveability is much improved.
Interesting, from memory the 4.2 on the shoot out days used to make about 340bhp so still probably a decent improvement. Driveability is more important really though, you notice that more these days will modern cars being so much better than they were 20 years ago…
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