NEW OWNER 4.5 AJP V8
Discussion
Good Grief Mossey,
I do hope that the Cerb lives up to your heritage
At the top of the Cerbera forum is a thread "List of TVR Cerberas owned by PH members",
It starts with instructions on how to update it.
No-one is a bigger Dullo than me so never be afraid to ask anything
P.S. That is ONE, BEAUTIFUL example
I do hope that the Cerb lives up to your heritage
At the top of the Cerbera forum is a thread "List of TVR Cerberas owned by PH members",
It starts with instructions on how to update it.
No-one is a bigger Dullo than me so never be afraid to ask anything
P.S. That is ONE, BEAUTIFUL example
Sigilobaphomet said:
No idea how to update owners list?
On a mission to iron out the 1800rpm stutter!!!
Previously T339 JTR if the previous owner is on here please get in touch!
EDIT: I think I've found the cause of the stutter, for me at least, answer posted a bit further downOn a mission to iron out the 1800rpm stutter!!!
Previously T339 JTR if the previous owner is on here please get in touch!
Looks very nice!
If you work out what to do with the owners list let me know
What ECU do you have? I've had an Emerald in the 4.5 for many years now & after a lot of messing about getting it running as nicely as possible I'm left with that annoying stutter at around 2,000rpm
I've had so many other problems over the last ten years I've forgotten if it used to have that stutter there when it was all original and a lot newer (we've had it for 24 years now).
I can't decided if I've just made it so smooth above & below that stutter it's more notable, or if it's just worse now.
I think Joolz has mentioned over the years that it is a problem area for them.
I'm assuming its something to do with the way the fuel sprays at the back of a closed butterfly on the 4.5 - at some point it has to transition from puddled fuel getting re-vaporised by heat & vacuum to the spray from the injectors making it round the small gap a the edge with out dropping out of suspension as a mist / spray.
I don't think it was as noticeable when I had decats & was running an AFR of 13.8 there, it seems a lot worse with the Cats back in & the mixture targeting 14.7 (as it would do in a standard MBE). I'm just in the process of trying it a little richer in that area again now, it seems a little better but I'm not sure how rich I can go with Cats in.
I tried a large range of ignition setting at that point but it made no difference (with a cat friendly mixture).
The 4.2 has its injectors on the more normal engine side of the butterflies so they just spray at the back of the intake valves all the time with no obstructions. I've got one sat here waiting to get rebuilt, the last one I did with 4.2 inlets was very noticeably much better at the 1800 - 2200 kind of area.....
Edited by Luckyone on Friday 4th October 09:18
TwinKam said:
FarmyardPants said:
Start by fitting another earth between the battery -ve terminal and the rocker cover
Rocker cover?...
. I measured a good few Ohms resistance between the two, so put a cable between them as a test - it fixed my lumpy idle and the car ran noticeably smoother. I left it there, although I agree the battery-chassis and chassis-engine earths should be fixed properly at some point. It runs under the airbox so quite discrete. I am famous for my bodges Worth a try anyway.
Sigilobaphomet said:
On a mission to iron out the 1800rpm stutter!!!
Edited by FarmyardPants on Sunday 15th September 08:26
FarmyardPants said:
TwinKam said:
FarmyardPants said:
Start by fitting another earth between the battery -ve terminal and the rocker cover
Rocker cover?.... I measured a good few Ohms resistance between the two, so put a cable between them as a test - it fixed my lumpy idle and the car ran noticeably smoother. I left it there, although I agree the battery-chassis and chassis-engine earths should be fixed properly at some point. It runs under the airbox so quite discrete. I am famous for my bodges Worth a try anyway.
Sigilobaphomet said:
On a mission to iron out the 1800rpm stutter!!!
My (pedantic) point was that your car has no 'rocker covers'... Edited by FarmyardPants on Sunday 15th September 08:26
Sigilobaphomet][url said:
On a mission to iron out the 1800rpm stutter!!!
We've had the 4.5 over 20 years now & I was thinking (since my last post) that I didn't remember the stutter ever being an issue when the car was much newer so it seemed unlikely it was an actual design issue. Throttle pots were mentioned by a helpful chap as the cure for him, so I got very excited as they were the one thing I hadn't ever changed. There are those nice new ones that cost a lot of money a good few people have found to be very good. I didn't really fancy spending £400 - £500 on them in the hope they may help, so wanted to look into it a bit more first.
Luckily my Emerald can log any input you want it to:
The pink (or purple?) line is RPM, the vertical white line is taking a sample at 1857rpm there, you can see the RPM line going very bumpy passed that point, when that annoying stutter starts.
However curved horizonal white line is the raw output of the throttle pot, if there was any noise or jumping on the output of the Tpot you'd see it on that line. (The increments of that output are about 0.01% of throttle movement, the normal throttle % you'd see on the MBE is the yellow line, you can see by comparison it has very big steps when it changes value)
I thought I'd at least take the tpot off to check how it operated off the car, watching that raw output I could see it was working perfectly well, no jumping of the output at all.
Taking it off reminded me I'd fitted bearings to the rear of the throttle bodies a couple of years ago as I was having a lot of issues with it running rough all over the rev range, they had made big improvements.
Good old Tamiya hop up parts are the cure (a misspent youth & now having my own kids can be useful) the 1510 bearing is an almost perfect fit in place of the O ring on the end of the throttle shafts:
There is a spare 1510 bearing on the cam cover there & there is one in place on the end of the shaft, it did need a single layer of silver foil type heat proof tape round the outside to be a nice snug fit in there, the centre is a perfect fit on the larger part of the throttle shaft you can't quite see. The others in the back have been fine for the last few years so I thought I'd try some on the front now too.
The only issue is that it sticks out a bit so it needs a 2mm thick spacer with a 15mm hole that can locate onto both the part of the bearing that's sticking out & the lug on the Tpot (that lug needed a tiny amount sanding off it so it sat nicely next to the outside of the bearing):
That ensures the pot is sitting exactly central on the end of the shaft, as it had been when the car was new but the slight amount of play that develops in the throttle shafts may cause some issues. The odd thing is that I couldn't see any fluctuations in the raw output from the pot before doing this mod. I think it must be the shafts bouncing about affecting air flow into the engine more than the readings from the pots. The amount of play in the shafts on the back end where the throttle linkages are was really bad, the movement on this one didn't seem like much but I could certainly feel some movement in the shaft before & non after. When I was doing the rears I had to take the shafts out completely, I found there was much more play at certain points, I only checked with the throttle completely shut, it may well have had a lot more play in the normal driving range.
I think this is one area the 4.5 will suffer more than the 4.2 as the injectors are constantly spraying fuel on the shafts where as the 4.2 shafts are way off back up the inlets & always seem to be covered in oil...
With bearings now on both ends of both throttle bodies the annoying stutter seems to have reduced to the point I can't feel it at all, I can still hear the engine isn't running totally smoothly, but it massively better to drive. The RPM line still looks noisy to me so that's something else on ongoing but at least it's finally a nice car to drive again!
If anyone wants to try it on their 4.5 just search for Tamiya 1510 bearings on ebay or somewhere, they don't need to be genuine the copies seem fine & they should be less than £1 each! (I didn't go for the rubber sealed bearings my son & I found they quickly fall to bits in his RC cars)
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