shunting/leaning out on cruise
Discussion
can anyone put me in the right direction. i have a 2000 model 450. when cruising at all speeds mainly lower though 35-45 mph is worst she is what appears to going lean, the only other way i can discribe it is this, if it was a carburettor car then i would feel as if it were a blocked air jet making it surge on cruise. when i just tickle throttle lean out goes, back to cruise and fault is back, being in the trade i am reluctent to throw lots of parts at it, have replaced plugs,caps,leads,rotor,coil already but i need to dig further i think. i have been told this can be normal, no way is this normal.any help would be appreciated.
Not exactly clear as to what the problem is but the usual answer around here is 'clean the stepper motor'.
I did this for the first time a few days ago and it made a world of difference to the smooth running and response of the car.
(My stepper was completely black with soot and looked like it had never been touched in the cars life)
A real quick and easy job provided you have a big enough spanner to unscrew it!
I did this for the first time a few days ago and it made a world of difference to the smooth running and response of the car.
(My stepper was completely black with soot and looked like it had never been touched in the cars life)
A real quick and easy job provided you have a big enough spanner to unscrew it!
Its basically down to the use of a plenum chamber with a long duration cam, so exhaust gets pumped back up into the plenum during the valve overlap and contaminates the fresh air being drawn into the cylinders. All the various "cures" involve reducing this effect, be it forcing the engine to run a bit richer, (not running the catalyst fuel map), adding plenum volume with a spacer, improving spark and / or timing to improve the burn with better HT components, or replacing the whole ECU and removing the AFM that does not work well with a longer duration cam at low speed. Mind you not even this is guaranteed to cure the issue, as ultimately you would be better off with separate throttle bodies so you dont get the cross contamination in the first place.
I had this problem when I bought my 450 last year. After looking at most other things it turned out to be my Vacuum Advance on the distributor leaking. I've replaced that and its much better now. May be worth a look and there are insructions on checking the vac advance if you search on here.
Cheers,
Nigel
Cheers,
Nigel
From what i can gather the only real cure for shunting is to fit after market ecu which can be properly mapped, fuel and spark.
I have also read that fitting a carb such as the Webber 500 can sort things. I know several on here have done and have good things to say about it. I know many are going to say fitting a carb is a step back 20yrs, but an aweful lot of threads on here are about running problems associated with the ecu and injection system. After all these componenets are a good few years old now and probably past their best.
I have also read that fitting a carb such as the Webber 500 can sort things. I know several on here have done and have good things to say about it. I know many are going to say fitting a carb is a step back 20yrs, but an aweful lot of threads on here are about running problems associated with the ecu and injection system. After all these componenets are a good few years old now and probably past their best.
A good part of the gains from fitting an after market ECU is you can remove the emission compliance that the 14CUX sticks to rigidly, and set the mixture thats best for the engine, not minimum pollutants. The Pre 1992 ECU set up did just this, but without the modern use of wide band lambda feedback, so it wont adapt if its mapping is not correct to start with, and it does need the correct chip to get the best out of it. As a simple test you can change the tune resistor under the dash to 470 ohms to switch fuel maps to the non catalyst mode, and then set a suitable idle / low speed mixture with the CO trim adjustment on the side of the AFM. This controls the mixture up to around 2400 rpm. Its OK for low speed testing, but you are likely to switch to a Range Rover fuel map so you do need to check the mixture at higher loads, or get an after market chip. I would think TVR power should have a range on non catalyst chips, or there is the Mark Adams Tornado range for more pennies. I don't know how well the physical catalysts will respond ( as in overheating) to the wider mixture ranges however if you run in non cat mode.
tvrkev said:
TVR BEAVER. you have placed a pic of a plenum and two fuel bodies, are you saying this is a fix to the fault.
Yes.. as Mark said above... It's overlap on cam's usualy feeding back into the Plenum and cross-contamination to other cylinders.... The option I pictured would solve it for sure... as your seperating the two banks
seriously... there are a few threads running on this now on here and the Griff section... good luck,, shunting is a pain!!
TVR Beaver said:
The option I pictured would solve it for sure... as your seperating the two banks
It's about as good as you'll get short of individual throttle bodies but it won't fully remove the problem assuming the firing order and angles remain as is. Top bit of lateral thinking 'though and the owner, and fabricator, are both regulars here 
Did anyone ever develop out the RV8 throttle body setup that Jools/Raceproved were working on? That looked sweet...
Pupp said:
TVR Beaver said:
The option I pictured would solve it for sure... as your seperating the two banks
It's about as good as you'll get short of individual throttle bodies but it won't fully remove the problem assuming the firing order and angles remain as is. Top bit of lateral thinking 'though and the owner, and fabricator, are both regulars here Did anyone ever develop out the RV8 throttle body setup that Jools/Raceproved were working on? That looked sweet...
v8 racing said:
to be honest that was actually done back in the eigthies by nck, original builders of the tvr engine, downside was the cost and nobody really wanted to pay for it, i think times have changed a bit and maybe there is a market for it?
Well, short of a mackled up bike donored set-up, it looks like about £3k+ is the TB cost of entry with a decent inlet manifold. Something that sits where the normal trumpet base lives but incorporates either butterflies or guillotine slides for maybe half(ish) that would walk out the door I'd say.'til then, I'll just drive round the shunts
tvrkev said:
thanks to everyone for all the info that has been given. i have found a local guy who deals in remapping & programming of ecu,s. gonna get in contact with him this week. your help has pointed me in the right direction for my problem too.
kev
Id be very surprised if he can do the 14CUX mapping, as its pretty unique,and Im certainly only aware of a couple of places in the UK that can do it, and even then mapping is unlikely to be the answer, or a suitable map would have been done years ago. kev
TVR Beaver said:
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