How smooth is yours...................
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at low traffic jam speeds?
Mine is very unwilling to crawl at say 20mph in the morning rush hour, can't just roll along in second as it's continually surging then slowing, you have to feather the clutch all the time at these speeds. Is there something needs doing to make it a bit more driveable in slow moving traffic or is this just the nature of the beast?
Mine is very unwilling to crawl at say 20mph in the morning rush hour, can't just roll along in second as it's continually surging then slowing, you have to feather the clutch all the time at these speeds. Is there something needs doing to make it a bit more driveable in slow moving traffic or is this just the nature of the beast?
My Griff 500 was sometimes a bit shunty when I got it - worse when cold. Since then the throttle pot has been set better, base idle reset (it was ticking over at 1400) and stepper motor cleaned and it is much better so could be worth a go. I can trickle along in 4th at 30 or so with no great problem once it has warmed up although when it is cold I can still get a little shunting.
Jim
Jim
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Its a combination of things really, as running a long duration cam shaft on a plenum chamber inlet system can lead to exhaust gas's contaminating the inlet charge during the overlap period. This mixture does not burn as well as it should so the car shunts. Anything that can improve the burn can help, such as improved inlet breathing, better ignition mapping, or a slightly richer mixture, but there is no one fix as such for all cases. The 14CUX ecu does not help as it tries to hold the mixture under tight control at low speed to limit the emmisions, but gets itself in a twist in the process that can lead to some fairly wide fueling corrections that adds to the problem. A simple test to see if this is a problem is to switch to the non catalyst fuel by changing the tune resistor to 470 ohms to stop the catalyst fuel control. This however not a long term fix, as the fuel map is likely to be for a Range Rover or like and not suitable for a 5ltr TVR engine. It may also damage the catalysts over time.
Its a combination of things really, as running a long duration cam shaft on a plenum chamber inlet system can lead to exhaust gas's contaminating the inlet charge during the overlap period. This mixture does not burn as well as it should so the car shunts. Anything that can improve the burn can help, such as improved inlet breathing, better ignition mapping, or a slightly richer mixture, but there is no one fix as such for all cases. The 14CUX ecu does not help as it tries to hold the mixture under tight control at low speed to limit the emmisions, but gets itself in a twist in the process that can lead to some fairly wide fueling corrections that adds to the problem. A simple test to see if this is a problem is to switch to the non catalyst fuel by changing the tune resistor to 470 ohms to stop the catalyst fuel control. This however not a long term fix, as the fuel map is likely to be for a Range Rover or like and not suitable for a 5ltr TVR engine. It may also damage the catalysts over time.
yellowgriff said:
Simon.b said:
captaindarling13 said:
at low traffic jam speeds?
Mine is very unwilling to crawl at say 20mph in the morning rush hour
I think some do, some don’t, mine is fine.Mine is very unwilling to crawl at say 20mph in the morning rush hour
ked about with thats you get.. stay standard Thanks for the various suggestions, I will do some investigating
My 4.5 does this. I believe it has the same cam as the 500's. I suspect it needs a mapping session amongst other things but wonder if this plenum spacer would work for me?
The higher the state of tune the more compromises you probably have to make at either end of the rev range I guess. It does go rather well out of traffic
The higher the state of tune the more compromises you probably have to make at either end of the rev range I guess. It does go rather well out of traffic
Edited by JamesK on Saturday 23 October 13:00
yellowgriff said:
Simon.b said:
captaindarling13 said:
at low traffic jam speeds?
Mine is very unwilling to crawl at say 20mph in the morning rush hour
I think some do, some don’t, mine is fine.Mine is very unwilling to crawl at say 20mph in the morning rush hour
ked about with thats you get.. stay standard My fathers 450 was standard and shunted like hell at times, recent cam change and induction review and changes along with checking everything is in spec, timed etc has solved it.
Sorry but standard does not mean no shunting at all, often the opposite. However major modifications are not always needed to resolve the issue, often it's a combination of rotor arm, cap, leads, ICV (stepper), induction, AFM outputs etc etc etc ....
"That's just a little bit of a sweeping generalisation "
.Bit harsh i know. But when they left the factory they all run well. Old age throws up problems and they are easier solved if car is standard. The only thing thats simple to give more BHP with out cams and the likes, Is super charger Or Nitros'
Open the bonnet you know what youve got & where to start,, with out dismantling,,Finding horror story.
.Bit harsh i know. But when they left the factory they all run well. Old age throws up problems and they are easier solved if car is standard. The only thing thats simple to give more BHP with out cams and the likes, Is super charger Or Nitros'
Open the bonnet you know what youve got & where to start,, with out dismantling,,Finding horror story.
yellowgriff said:
Simon.b said:
captaindarling13 said:
at low traffic jam speeds?
Mine is very unwilling to crawl at say 20mph in the morning rush hour
I think some do, some don’t, mine is fine.Mine is very unwilling to crawl at say 20mph in the morning rush hour
Having read this forum for a few years now it is very apparent that those who seem to have the most problems invariably drive a car modified in some way. There are a few who obviously understand the niceties of mapping etc. etc. and those that want to generate more power for competition, fair enough, but for the majority surely 270 BHP in a car weighing just over a ton is enough power on the road for anyone.
Regarding the instability caused by "Engine braking" if you lift off suddenly with that much power and a light back end not surprising that the car becomes unstable. I have been told that the Torque characteristics of a V8 emphasises this effect wheras a straight 6 is much more forgiving, suggested as one reason PW opted for a straight six on later cars, but stand to be corrected.
Edited after DNB,s valid corrections
Edited by Loubaruch on Sunday 24th October 09:45
Loubaruch said:
for the majority surely 300 BHP in a car weighing less than a ton is enough power on the road for anyone.
Good post apart from the quoted section. I get what you are trying to say and tend to agree, but a standard Griff 500 weighs in at about 1080kg and has about 270bhp on average. Not less than a ton and not 300bhp. You need a few mods to get there, and if you don't get too greedy, the car can still be smooth and tractable even with significant changes to standard. Gassing Station | Griffith | Top of Page | What's New | My Stuff