Engine Balancing
Discussion
I just want to put in my tuppence worth on balancing the AJP V8's.
I know a lot of people use air flow meters in conjunction with the software - and that's fine if you want to get each cylinder matching the others exactly, but for most people it's not about eking out the absolute maximum performance. It's just about achieving a smooth running engine. For this you just need to get each bank sucking the same amount of air and burning the same amount of fuel - balanced (oh yes!, within adaptive range).
This is really easy if you plug in a pair of vacuum gauges.
I've used these for years to balance carbs on motorbikes. I suddenly realised that the same principal applied to balancing the banks of an AJP V8.
On the 4.2 there are tapings already available for connecting vacuum gauges - the vapour recovery connections at the rear of intake manifolds. (I don't know about the 4.5, but I suspect there are similar tapping's).
Plug in a pair of vacuum gauges and adjust the throttle rod until both gauges read the same.
Now set both throttle pots to the same value. These are at 20.1 - just off picture.
This is an iterative process - so once you reset the throttle pots, you might need to re-sdjust the throttle linkage. When the vacuum gauges read the same, and the throttle pots read the same - both banks are sucking the same amount of air, and burning the same amount of fuel. Simple.
Now - look at the adaptives. If they are positive - it means the ECU is trying to add more fuel. So, increase the throttle angles of both banks (small amounts - 0.2 at a time). If they are negative - decrease the angle of both banks.
I've used this procedure for years - and its really easy. You can balance the engine in about 30 mins - when its warmed up (excluding the removal of panels etc.). It's also totally visible - giving immediate feedback.
The use of vacuum gauges can also indicate other engine issues. Sticky valves etc. Read up about them. They're really useful. Just a thought. . .
I know a lot of people use air flow meters in conjunction with the software - and that's fine if you want to get each cylinder matching the others exactly, but for most people it's not about eking out the absolute maximum performance. It's just about achieving a smooth running engine. For this you just need to get each bank sucking the same amount of air and burning the same amount of fuel - balanced (oh yes!, within adaptive range).
This is really easy if you plug in a pair of vacuum gauges.
I've used these for years to balance carbs on motorbikes. I suddenly realised that the same principal applied to balancing the banks of an AJP V8.
On the 4.2 there are tapings already available for connecting vacuum gauges - the vapour recovery connections at the rear of intake manifolds. (I don't know about the 4.5, but I suspect there are similar tapping's).
Plug in a pair of vacuum gauges and adjust the throttle rod until both gauges read the same.
Now set both throttle pots to the same value. These are at 20.1 - just off picture.
This is an iterative process - so once you reset the throttle pots, you might need to re-sdjust the throttle linkage. When the vacuum gauges read the same, and the throttle pots read the same - both banks are sucking the same amount of air, and burning the same amount of fuel. Simple.
Now - look at the adaptives. If they are positive - it means the ECU is trying to add more fuel. So, increase the throttle angles of both banks (small amounts - 0.2 at a time). If they are negative - decrease the angle of both banks.
I've used this procedure for years - and its really easy. You can balance the engine in about 30 mins - when its warmed up (excluding the removal of panels etc.). It's also totally visible - giving immediate feedback.
The use of vacuum gauges can also indicate other engine issues. Sticky valves etc. Read up about them. They're really useful. Just a thought. . .
Wow, this is very helpful.
I have a 4.5 and absolutely hate using the synchrometer because you have to measure one cylinder at a time and it seems like fueling is always moving around a bit. Having ‘always-reading‘ vacuum gauges would be a great solution.
I haven’t noticed a tapping point per se, wouldn’t it have to be somewhere on each air box? The 4.5 only has vapour recovery on the offside box and just a hole at the rear of the near side box (for the ECU pressure sense hose).
Suppose I could just drill a hole in each box and screw in a valve?
Adjusting the throttle link bar is a bit of a pig without removing the induction pipes (still have the large purple ones), but not having to take off all the induction to do a tune-up would be a great time (and hassle) saver.
I have a 4.5 and absolutely hate using the synchrometer because you have to measure one cylinder at a time and it seems like fueling is always moving around a bit. Having ‘always-reading‘ vacuum gauges would be a great solution.
I haven’t noticed a tapping point per se, wouldn’t it have to be somewhere on each air box? The 4.5 only has vapour recovery on the offside box and just a hole at the rear of the near side box (for the ECU pressure sense hose).
Suppose I could just drill a hole in each box and screw in a valve?
Adjusting the throttle link bar is a bit of a pig without removing the induction pipes (still have the large purple ones), but not having to take off all the induction to do a tune-up would be a great time (and hassle) saver.
Edited by Imran999 on Sunday 9th August 05:42
Imran999 said:
Suppose I could just drill a hole in each box and screw in a valve?
No, the vacuum is only created behind the throttle butterfly valves - so the tapping must be on the intake manifold between the butterfly valves and the cylinder intake port. On the 4.2 there is a common channel connecting all intakes together. The tapping's are on this.
It would be great to see a short video on this procedure. I’m new to engine work and things like set throttle bodies to, and adjust values is an unknown to me. But great info for those who are used to doing engine work. Maybe I should just leave it alone but I always like to learn and it would be good to be a lengthy to keep the engine in tune without running to my service centre which is a 250 mile round trip.
I don't have any knowledge regarding the 4.5 induction setup, however, from your photo - the four pipes going to the cross connector look like the vapour recovery pipes. One of them should go to the carbon capture tank in the rear offside wheel well. The fourth one should go to the airbox with the crankcase oil vent.
If this is the case, and the connection to no's 1 & 2 trumpets are behind the butterfly valves i.e - between the valves and the inlet ports - then you should get a genuine engine vacuum reading from those tapping's. I've tried to find a more detailed photo of the 4.5 manifolds, but unsuccessfully. Perhaps another PH'r with a 4.5 can confirm this.
My gut feeling is - YES. I don't see any reason why the 4.5 should operate any differently from the 4.2. Just slightly different layout.
Gordon
If this is the case, and the connection to no's 1 & 2 trumpets are behind the butterfly valves i.e - between the valves and the inlet ports - then you should get a genuine engine vacuum reading from those tapping's. I've tried to find a more detailed photo of the 4.5 manifolds, but unsuccessfully. Perhaps another PH'r with a 4.5 can confirm this.
My gut feeling is - YES. I don't see any reason why the 4.5 should operate any differently from the 4.2. Just slightly different layout.
Gordon
Just pull the pipes off from the connectors at 1 & 2 trumpets and connect the vacuum gauges there.
The vapour recovery only pulls vapour from the petrol tank due to hot fuel returning from the fuel rail (also pulls oil vapour from the catch tank). It's all part of trying to make the engine more 'green'..
The pipes can be left hanging free when the vacuum gauges are connected. Makes no real difference. Permanent 'T' connectors are not necessary.
The vapour recovery only pulls vapour from the petrol tank due to hot fuel returning from the fuel rail (also pulls oil vapour from the catch tank). It's all part of trying to make the engine more 'green'..
The pipes can be left hanging free when the vacuum gauges are connected. Makes no real difference. Permanent 'T' connectors are not necessary.
natben said:
It would be great to see a short video on this procedure..
Natben - Yeah - I'd like to post a video. Would make it a bit clearer. Unfortunately I'm pulling the engine at the moment. I discovered some 'sparkle' in the oil at the last change, and to be honest I've been nursing the engine for a couple of years. With this year being a complete non-event, I've decided to finally go for a full rebuild. I don't expect to be up and running again 'til next spring.The next time I perform this procedure I'll try to make a vid of it.
I know the issue of balancing the engine keeps popping up - so this post was purely to give my take on it. If it helps someone, then job done.
G.
Funnily enough that’s what I’ve just completed. I did a 12k service a couple years ago and was concerned about shim thickness. That was proven valid as it went on to chew a shim. Luckily it didn’t rinse it round the oil system.
Initially just the heads needed a refresh but then when I dug further it really needed rings, bearings etc...Just need my new lambdas to arrive!
Initially just the heads needed a refresh but then when I dug further it really needed rings, bearings etc...Just need my new lambdas to arrive!
Bogsye said:
Just need my new lambdas to arrive!
Here's hoping your new lambdas will sort all you probs. I replaced mine last year and it fixed my recurring AFR errors. I was hoping for a good 'Cerbera' year this year, but it's not been what anyone expected. I had the seats re-upholstered last winter and was really looking forward to this years driving. Hey-ho!I think I 'm going to go for a professional build. I've owned this car for 15 years and while I'm sure I could do it myself - I also think there's something I'll probably miss. Also, in terms of equipment and resources, I'd probably need to call on professional help at numerous points in any case. I don't want to start chasing more problems after all the effort. So - top to bottom refurb + new timing chain etc. Oh - and gearbox rebuild/check. There was sparkle in that oil as well. I've just drained it. :-(
Next years going to be fun :-)
G.
I have my fingers crossed for the lambdas too. On the plus side after the clutch debacle the gearbox that I did consider seems much happier, which is a pleasant bonus. Forgot I did the timing chain, bearings and all the seals.
I did a good bit of reading in preparation for it, so I’m hopeful I’ve covered the bases. What would Cerbera ownership be with out anxiety...
Even has a new set of sensible size PS4’s all round, so I think it should be a much more pleasant driving experience.
Looking forward to getting it out, shaken down and run in.
Good luck with your rebuild, whichever route you go.
Cheers,
Brian
I did a good bit of reading in preparation for it, so I’m hopeful I’ve covered the bases. What would Cerbera ownership be with out anxiety...
Even has a new set of sensible size PS4’s all round, so I think it should be a much more pleasant driving experience.
Looking forward to getting it out, shaken down and run in.
Good luck with your rebuild, whichever route you go.
Cheers,
Brian
notaping said:
Bogsye said:
Just need my new lambdas to arrive!
Here's hoping your new lambdas will sort all you probs. I replaced mine last year and it fixed my recurring AFR errors. I was hoping for a good 'Cerbera' year this year, but it's not been what anyone expected. I had the seats re-upholstered last winter and was really looking forward to this years driving. Hey-ho!I think I 'm going to go for a professional build. I've owned this car for 15 years and while I'm sure I could do it myself - I also think there's something I'll probably miss. Also, in terms of equipment and resources, I'd probably need to call on professional help at numerous points in any case. I don't want to start chasing more problems after all the effort. So - top to bottom refurb + new timing chain etc. Oh - and gearbox rebuild/check. There was sparkle in that oil as well. I've just drained it. :-(
Next years going to be fun :-)
G.
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