3200 throttle body - lock down project.

Oneball

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11,075
I’d be surprised if the choke profile has that much of an effect. It’s only usually noticeable on carbs as it affects the vacuum they impose on the fuelling jets. Are you sure that both Maserati and Volvo throttle bodies open the same amount at a given pedal depression?
 

davy83

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2,809
I was surprised and really was hoping to just use the Volvo parts as is. However the low throttle area on the Volvo unit is shaped to restrict air flow presumably to make idle and low throttle control better where the Maserati unit is a straight open choke. The Volvo unit makes the car seem sluggish off the line and does not feel right at all (and creates a lot of air noise). I guess the Maserati ECU expects a certain reponse for a given flap opening, and its not getting that with the Volvo unit. The car drives without errors with the stadnard volvo unit but it does not feel right at low throttle. The idle is very steady though. I reckon it needs to be fixed to make it a good replacement part.
 

davy83

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2,809
Ok update on this project. I can now pretty well take a Volvo unit and convert it for Maserati 3200 use, and its good, drives well and no errors. I can add contactless sensors to the ETM and this also works although there are some issues with the Sacer sensors which causes fluctuation problems and makes me wonder if a lot of the unstable idle problems are because of a contactless upgrade. I am looking at this and hope to make some design changes to make this reliable, and maybe even try to make the 3200 idle rock steady like it really should be.
I can control the amout of instability at idle, and responsiveness with the machining of the choke profile, and I have what I think is a decent solution.
I have also successfully taken a stock 3200 ETM and stripped it completely and rebuilt it with newer parts from a donor Volvo unit and this also works well, but takes a lot of work. I have yet to do an extended test drive with this one but it looks very promising. The magnet assembly on the newer ones has been changed quite a bit and has an aluminium sheild round it to prevent issues with bits of magnet breaking off I guess, and generally looks a lot better made.
I am building an automated test rig which will instrument every aspect of the ETM including air flow so I can map the modified ones to match exactly the profile of the OEM version, and also measure any sticking and indeed the response time and sensor output matching. This will be ready within about 10 days. This will also allow me to run testing on any throttle body and determine exactly what its doing, and also allow me ot get a level of consistency with these modified ones.
So if any one has problem with their throttle body give me a shout, I have some options, I can replace it or rebuild the old one with newer parts. I will post some of the many throttle bodies I have now (I have purchased 6 now for various experiments, and they all work!!!) on e-bay too so anyone can get these.
 

davy83

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2,809
I know you have all lost interest in my lock down project, but i have made some interesting observations in my testing. I am wondering how many people have a contactless upgrade and have unsteady idle or problems driving and control, especially at low revs?
It seems we have been upgrading these ETMs with hall effect contactless throttle position sensors and yes this stop them wearing out, but they are very prone to interference from magnetic sources , like err well the throttle body motor!!! I have converted 4 of these with contactless rotary sensors and 2 of these were fine and 2 had instability problems after the upgrade, subtle but there nevertheless.
I have had a contactless upgrade on my throttle body for many years and its been very reliable but I have had occasional unsteady idle and odd revving of the engine, and I now see its been the hall effect rotary sensor all along. I have now had various other throttle bodies (8 or 9 in total) on my car and its clearly not the car, it really is the throttle body. With the right ETM the car starts like a rock and idles rock steady.
I have not worked out the perfect solution to this but i am working on it. It may actually be better to put a new high reliability contact, carbon track rotary sensor on the ETM which is not affected by the motor.
 

ScottH

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216
Like the brake thread I read everything but have no idea what most of it means, admire the work put in any case.
 

Lozzer

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2,280
i have made some interesting observations in my testing. I am wondering how many people have a contactless upgrade and have unsteady idle or problems driving and control, especially at low revs?
.

Hi Davy, i have the unsteady idle issue, its not severe and not all the time either, no driving issues though. Can the hall sensor not be shielded somehow?
 

davy83

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2,809
i am looking at shielding, and also optical encoders, but there are some serious issues with both these routes. I hope to find a decent solution of some sort.
Optical encoders generate pulse streams and i need voltages, so I would need some electronics to make it work, i am talking to a few different sensor companies to see what are the viable options and also looking at shielding or modifying the existing sensors to remove this issue.
some of the ETM's work quite well with the hall effect sensors but a 50% success rate is not a good place to be.
 

Rex B

Member
Messages
657
Davy
Keep up the good work with a new TB now being over £3k your work on finding alternatives and affordable replacements will save many a 3200 from the scrap yard.
Rex B
 

Lozzer

Member
Messages
2,280
i am looking at shielding, and also optical encoders, but there are some serious issues with both these routes. I hope to find a decent solution of some sort.
Optical encoders generate pulse streams and i need voltages, so I would need some electronics to make it work, i am talking to a few different sensor companies to see what are the viable options and also looking at shielding or modifying the existing sensors to remove this issue.
some of the ETM's work quite well with the hall effect sensors but a 50% success rate is not a good place to be.
Why do some TB work flawlessly and others not when they are essentially the same? Is it down to pairing the TB electronics to a specific ECU?
Just to add, you know I appreciate the work you do with the 3200, every 3200 owner does mate.
 

davy83

Member
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2,809
Why do some TB work flawlessly and others not when they are essentially the same? Is it down to pairing the TB electronics to a specific ECU?
Just to add, you know I appreciate the work you do with the 3200, every 3200 owner does mate.
its a very good question sir. And i am not entirely sure. Being an interference problem it will be affected by many variables like the way the motor windings are perhaps but more likely down to differences in the hall sensors and indeed the differences in the permanent magnet that is used to activate them. There may be some simple "good practice" that might solve this, but its not obivous to me so far. i am sure this can be sorted out tho.
And thanks for your supportive words sir, but I am enjoying this, so its not a trial really!!! :)
 

happydaze

Member
Messages
561
I am in awe of your dogged tenacity, Davy. My '01 3200 GT seems to be fairly well-behaved at present (he says whilst firmly gripping the wooden table), however there could be TB trouble ahead, no doubt. Being 'old-school', my only way of attacking this problem would be to attach four Weber carburettors - as per the '71 Indy that I had many years back...:)
 

Oishi

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Messages
825
At the risk of sounding like an idiot once again, I'll offer my 2cents worth. We have had some success with converting old CNC machines to modern optical encoders by using a DAC (usually a 32bit) and rewriting the calibration algorithm.
 

Danny

Member
Messages
442
Davy, very interesting. I am fully contactless and I always wondered why the V8 would not be rock steady whilst stationary. I remember to have seen YT videos where owners would put a coin on the side on top of a V8 engine, and I believed that the rough idle of the 3200 was just due to the nature of the (high performance) Italian Maser engine. But if I understand your above post correctly, then you are suggesting that this could be caused by the design of the contactless conversion. If you could find a solution for the rough(ish) idle, then I would definitely be interested!
 

davy83

Member
Messages
2,809
Davy, very interesting. I am fully contactless and I always wondered why the V8 would not be rock steady whilst stationary. I remember to have seen YT videos where owners would put a coin on the side on top of a V8 engine, and I believed that the rough idle of the 3200 was just due to the nature of the (high performance) Italian Maser engine. But if I understand your above post correctly, then you are suggesting that this could be caused by the design of the contactless conversion. If you could find a solution for the rough(ish) idle, then I would definitely be interested!
I am beginning to think just that sir. I have had my car for 14 years and its always had a tendency to idle slightly unsteady, and like you i have had a couple of TVR V8's that ticked over like a metronome and I just put it down to the highly strung engine in the Maserati, but it looks like its probably this stupid throttle body. I have one in my car now and it ticks over absolutely steady. I have another couple on my bench where it drifts gently up and down!! its not the engine!!
 

MRichards

Member
Messages
278
FWIW I have recently fitted a new TB and there are no idle problems. So we may assume the strange drifting of the idle up & down is due to prolonged useage ? I also have a rebuilt TB from XeMODeX in Canada which idles perfectly. It seems to me there are some subtle differences of which we are currently unaware.