Manifold vacuum
Discussion
Hi all, recent owner of a Chim 500. My car has an ACT twin plenum with no existing spare vacuum ports on the plenum base (just the two for the brake servo and carbon canister). As I don't want to disturb the plenum, for fear of introducing a vacuum leak, to access the fuel pressure regulator vacuum hose, I'm thinking aout teeing into either the brake servo or carbon canister hose to get manifold vacuum to improve the idle and shunting. Is there any benefit of using one against the other?
Hi mate, saw your post on FB too.
No difference between those two for this application - they are both open routes to the manifold.
You could even go a further step to see if the carbon can is still working (by applying 12V to its connectors and listen for a solenoid/valve opening sound), which might provide a reason to strip it out and use that port for dizzy advance.
Then for MOT, simply disconnect it, and run the car with no vacuum assisted advance for a day.
It might be a bit sluggish, but should pass the emissions test.
No difference between those two for this application - they are both open routes to the manifold.
You could even go a further step to see if the carbon can is still working (by applying 12V to its connectors and listen for a solenoid/valve opening sound), which might provide a reason to strip it out and use that port for dizzy advance.
Then for MOT, simply disconnect it, and run the car with no vacuum assisted advance for a day.
It might be a bit sluggish, but should pass the emissions test.
I've heard of it being blocked too.
Depends if you want ported vacuum signal or full manifold vacuum - which is arguably better for the engine running through lower revs.
But if you can unblock it, then (without having to do anything special) you will at least learn how the engine responds to having vacuum bringing in advance
Depends if you want ported vacuum signal or full manifold vacuum - which is arguably better for the engine running through lower revs.
But if you can unblock it, then (without having to do anything special) you will at least learn how the engine responds to having vacuum bringing in advance
IrishAv8or said:
It's strange, I can blow through the tube when connected to the plenum (albeit it's a very light hiss). I am changing over to manifold vacuum (teeing into carbon can hose) tomorrow and will just plug that vacuum for the test allowing it back to 12 BTDC and emissions-friendly.
I set mine to a base of 8° BTDC with no vacuum advance.With full manifold vacuum, it pulls up to 18-20° BTDC.
I believe the engine will take more, but expect around a 10° advance to be added, clearly a decent timing light is your best friend in this plight!
Hi
I have recently changed my vacuum hose as at one end the connector had broken
Not sure how long it’s been like that.
I renewed the vacuum advance module a few years ago as the existing one was not working.
Since the hose change car seems to be running smoother and reduced shunting.
Time will tell as I used the car much since then.
Everything is standard
I have recently changed my vacuum hose as at one end the connector had broken
Not sure how long it’s been like that.
I renewed the vacuum advance module a few years ago as the existing one was not working.
Since the hose change car seems to be running smoother and reduced shunting.
Time will tell as I used the car much since then.
Everything is standard
Following many of the old threads on the subject of vacuum, I've acceeded to ChimpOnGas's compelling argument about using manifold vacuum and I've teed into the carbon can vacuum line. I'm getting about 6-7 degrees of advance using manifold vacuum (10 deg static and 16 deg w/vacuum with the plenum vacuum port blocked off). Despite this, I'm still getting significant shunting in the 1200-1800 rev range, so I'll have to look elsewhere. I've checked for air leaks and I've tried another stepper motor. It's probably time to get more educated eyes to take a look at it.
Shunting is a world pf pain. Its what happens when you put a sports cam into an old plenum based engine design and slap on emission control as well that tries to hold the mixture at 14.7:1, which is really too lean for the old Rover V8. All these things lead to poor air flow and cylinder filling at low RPM plus poor burn due to the over lean mixture. You will find a raft of " fixes" that basically boils down to anything that improves burn and ignition, so first place is to make sure the ignition and plugs are good. Also check long / short term fuel trims with RoverGauge to make sure you dont have lots of trim correction, that might flag up a bad sensor input to the ECU. Assuming everything is basically OK, the most reliable fix is get rid of the emission control set up by switching from the "white" catalyst fuel map with lambda probes (closed loop) , across to the older "green" fuel map that has manual mixture control (open loop) on the side of the AFM. This means you can run richer at nearer 13.5:1 at low RPM so the engine is much happier.
Switching maps does require a ECU chip change in the ECU to put a TVR non catalyst tune in the green map location (in stock form its still Range Rover in the TVR chip) but maps are free thanks to Steve Sprint and just need blowing into an Eprom. You also have to change the tune resistor in the ECU wiring loom to make the ECU change the map it reads from.
However.... Loss of lambda feedback can result in emissions being too high come MOT time, so the tune resistor needs to be swapped back to the catalyst "white map" before the MOT. The tune resistor can easily be made switchable with a couple of resistors and a switch to short one out as needed to alter the value, The ECU will quite happy switch maps with no more than an ignition cycle between switching.
The physical catalyst does not appear to be harmed by running a non catalyst map, as even in catalyst tune the ECU goes open loop above 3400 RPM.
Map Links:
http://www.remap-14cux.uk/bins/
Basic fuelling of the 14CUX.
http://www.g33.co.uk/pages/technical-fuel-injectio...
One for a long read....
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Switching maps does require a ECU chip change in the ECU to put a TVR non catalyst tune in the green map location (in stock form its still Range Rover in the TVR chip) but maps are free thanks to Steve Sprint and just need blowing into an Eprom. You also have to change the tune resistor in the ECU wiring loom to make the ECU change the map it reads from.
However.... Loss of lambda feedback can result in emissions being too high come MOT time, so the tune resistor needs to be swapped back to the catalyst "white map" before the MOT. The tune resistor can easily be made switchable with a couple of resistors and a switch to short one out as needed to alter the value, The ECU will quite happy switch maps with no more than an ignition cycle between switching.
The physical catalyst does not appear to be harmed by running a non catalyst map, as even in catalyst tune the ECU goes open loop above 3400 RPM.
Map Links:
http://www.remap-14cux.uk/bins/
Basic fuelling of the 14CUX.
http://www.g33.co.uk/pages/technical-fuel-injectio...
One for a long read....
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Thanks for the info. I have new leads and plugs (BPR6ES @ 0.9mm) and no extenders. The 500 had a body off restoration in 2019 and, at the same time, had an ACT twin plenum intake, 885 cam + chain, Bosch AFM and upgraded injectors etc and (allegedly) a Mark Adams chip. When I opened the ECU, it has an unmarked PROM with no sticker or markings, just the erasure window (which is concerning). I do have Rovergauge and have downloaded the EPROM binary (who's ID suggests it's a 4.2 chip). The car has two new lambda sensors and the stepper motor is clean (I tried a new stepper, but it gave a permanently elevated idle, so changed back). The TPS voltage was a little high, but I reset it to 0.33V. AFM working as expected. I did have an air leak around the carbon fibre intake cover, but I've sealed it (and smoke tested it) and there's no improvement in the shunting. I've tried various advance settings both with ported and manifold vacuum (current config). Being in Southern Ireland, it's not easy to get to any of the Joolz's of this world. I do have a local rolling road where there is a lot of racing and engine building experience, so I might pop there to get the AFR checked across the rev range. I'll also do some fresh Rovergauge logs to check how much trimming is taking place. I've no issue changing to a green tune (not sure if I have precats as well as the main cat in mine). The car has just been through its test and, being 30 years old now, the next test isn't for 2 years, so reverting to the white tune won't need doing until then. Clearly, I don't want to damage the cat(s). If I have to change the manifolds and Y piece, I'll also need to change the main silencer box as it's currently sleeved and don't need it any louder :-)
ACT may have supplied the Tornado chip as its known as they supplied the plenum and maybe the Afm upgrade.
885 is a Powers product from memory.
Any idea who did the engine work?
Worth a chat with ACT if your struggling, may be worth checking the fuel pressure etc but this should have been dialled in when it was modified.
885 is a Powers product from memory.
Any idea who did the engine work?
Worth a chat with ACT if your struggling, may be worth checking the fuel pressure etc but this should have been dialled in when it was modified.
The engine work was (presumably) done by Amore in-house as I have the receipt. It’s done less than 2,000 miles since it was all installed. I’ve contacted both ACT and Powers but haven’t got any further with it (I’m waiting on Tim to come back to me with the procedure setting up base idle on a twin plenum system). When I purchased the car in September I was told that it needed mapping to suit the upgrades but, even then, it wasn’t shunting as badly as it is now. In terms of it being a Tornado chip, I would have expected some ID on the chip, not just a blank chip with open erasure window. I have the binary file of the chip if anyone’s clever enough to analyse it?
Amore claim they don`t do any in house work so that`s a bit odd.
My be beneficial for you to purchase Rovergauge and have a look at the basics, you can run a log and let someone here analyse it for you to see if there are any clues.
If someone has told you it needs mapping then sadly it probably does.
With these cars sometimes its better to hand it over to a 14cux specialist even if it means a bit of travelling, but in your case that may be difficult.
You could consider giving it to someone like Jools to let him work his magic or even go one further and fit aftermarket management, you wont regret it to be honest if its a keeper and it dramatically improves the cars.
Obviously its beneficial to find tuners locally but you may have someone, Megasquirt is a nice project if you were able to diy it.
My be beneficial for you to purchase Rovergauge and have a look at the basics, you can run a log and let someone here analyse it for you to see if there are any clues.
If someone has told you it needs mapping then sadly it probably does.
With these cars sometimes its better to hand it over to a 14cux specialist even if it means a bit of travelling, but in your case that may be difficult.
You could consider giving it to someone like Jools to let him work his magic or even go one further and fit aftermarket management, you wont regret it to be honest if its a keeper and it dramatically improves the cars.
Obviously its beneficial to find tuners locally but you may have someone, Megasquirt is a nice project if you were able to diy it.
Edited by Belle427 on Wednesday 7th January 06:30
Edited by Belle427 on Wednesday 7th January 06:31
IrishAv8or said:
The engine work was (presumably) done by Amore in-house as I have the receipt. It s done less than 2,000 miles since it was all installed. I ve contacted both ACT and Powers but haven t got any further with it (I m waiting on Tim to come back to me with the procedure setting up base idle on a twin plenum system). When I purchased the car in September I was told that it needed mapping to suit the upgrades but, even then, it wasn t shunting as badly as it is now. In terms of it being a Tornado chip, I would have expected some ID on the chip, not just a blank chip with open erasure window. I have the binary file of the chip if anyone s clever enough to analyse it?
Mark Adams chips are normally plugged into an piggy backed encryption device, plus have his label on them, so you don't have one of those. All your mods would need a remap to match the new airflow to the bottom of the fuel table. Going back to the shunting, the whole lambda feedback on the TVR is a bag of worms. You have your probes after the pre cat so this slows down the response when the gas flow velocity is slower, and its far from quick in the first place with 1980's tech in the ECU. The ECU only measures the mixture at idle to set the long term, and less stable airflow with a long duration cam means it does not always get a good reading. Even with a decent long term trim, the moment the car goes above idle only the short term trim can correct things. If it has to make big changes, it does so in multiple steps that can lead to significant over shoot, that makes shunting far worse.As an experiment you can still try the green tune, as this will at least lead to a stable mixture, even if the map is not perfect. Ideally you need an AFR meter and wide band probe to get an accurate AFR reading, but Rovergauge will at least give you the CO trim voltage on the side of the AFM. This is normally around 1.2 to 1.6 volts but a wrong map can throw this out. As a basic set up on the green, get the engine warm, and read the CO trim on RG. As you alter the voltage the mixture will change, the lower voltage the leaner. Do this by ear by winding the voltage up- engine will smell of fuel and run rough as it becomes too rich. Then wind the voltage down until the exhaust becomes acrid, and the engine starts to rock as it becomes too lean. Then wind the voltage back up until the idle smooths out, and about 1 turn more. Then try a test run.
In terms of Maps a Mark Adams chip will have both white and green tune for your engine set up. If you have paid for one, you need to make sure you have it as they are about £400. I hope ACT can help you as I thought the upgrades where sold as a kit of parts? Far as I know all Mark Adams chips have both the white and green tune for whatever set up you have, so you can switch maps quite happily. If you do have a TVR map for the 20 AM, the aifrlow scaling will be completely wrong as the voltage is about 10 % lower than the 5AM so it wont use the whole map and the fuel points will be incorrect. You can send me your .bin if you like, and ill see if it looks like a 4.2.
Edited by blitzracing on Wednesday 7th January 10:02
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