Who's had their throttle bodies modded with bearings?

[BGB autosport]

From what other people have said and from what mine appear the wear in the bodies can create a mechanical ticking/rattling sound from the throttle body.

[Robertjp]

BGB autosport said:

From what other people have said and from what mine appear the wear in the bodies can create a mechanical ticking/rattling sound from the throttle body.

Yep, same sort of noise here,rattling. Thought it was the engine!!

[Buffoon]

Another job on the list then. Amazingly I am worried that curing throttle noise will tune my ears into engine noise even more. 1 worry cured is another worry doubled.

[BGB autosport]

Decat and carbon cans should sort that.

[so called]

BGB autosport said:

Decat and carbon cans should sort that.

and sleeves

BGB autosport, just noticed your occupation..........Health, Safety and Environment manager.
Decat and carbon cans indeed !!!
You dont take your work home at the weekend then.

[Tuscanuwe]

Health, Safety and Environment manager."

"""Loud pipes save lives"""

Uwe

[BGB autosport]

I pretty much got my job because im the unsafetest person around, worked on the shop floor and know all the tricks and what a pain in the arse elf and safety can be.

Hence i now work for a company that had a crap H&S record which is now excellent, the guys do what they are asked and pretty much every thing i have put in place has improved not restricted production. Realistic H&S works, idiots that love cotton wool dont.

I also got seen doing donuts in the works car park by the general manager....

[so called]

BGB autosport said:

I also got seen doing donuts in the works car park by the general manager....

And your excuse....."now dont let me see you doing this".

[PetrolHeadPete]

BGB autosport said:

From what other people have said and from what mine appear the wear in the bodies can create a mechanical ticking/rattling sound from the throttle body.

Question: the play we are talking about...is it the end-float of the butterflies plus shafts...or is it the radial shaft-in-too-big-a-hole play. The one that causes the erratic running is which one ?

Got mine apart for modifying right now.

[so called]

Its the shaft in too big a hole.
The early models didnt have any bushes fitted so steel shaft in aluminium casting results in quite a bit of wear.

[Stunned Monkey]

It's thread resurrection time!

I figured it better to comment on this thread, being the best one of its type Google found…

My “new” Cerb has some throttle issues, and I think I may be staring down the barrel of worn throttle bearings (or lack of them).

I am a mechanical engineer by trade and I’m concerned by the option of replacing with rolling bearings – roller bearings offered by RG & Str8six and ball bearings currently on offer on eBay.

Robertjp said:

The absolute engineering solution seems to have been undertaken by Dreadnought TVR, I had a good chat with them and their understanding of this problem is extremely good. Roller bearing fixes are done by Str8 Six and Racing Green, but talking to Dreadnought a roller bearing fix isn't ideal either due to issues around low stiction with bearings and a further vibration caused by airflow

This is the best comment so far on this subject. Rolling bearings are designed to rotate by a minimum amount at regular intervals – usually the angle over which one rolling element meets the place taken by its immediate neighbour. This ensures distribution of lubrication. If the rolling element stays in one place and vibrates, the grease gets shunted from side to side and over time, you’ll get metal-to-metal contact and a wear effect known as false brinelling.

http://en.wikipedia.org/wiki/False_brinelling

It is this effect which leads car dealers to have to change out wheel bearings on brand new fresh-off-the-transporter cars. Also, bearings used in steering racks are very specifically designed by bearing manufacturers.

At idle, the same elements in our throttle bodies live at the same position in the bearings for long periods and vibrations are considerable…

IMO, this is a job for a plain bearing. Oil impregnated phosphor bronze, or one of the high fallutin’ polymer type bushes on offer from companies such as Igus.

There has been some debate on the importance of these bearings and why play in the shafts cause so much trouble. This engine is mapped by TPS which is very unusual in a road car. All engine management systems need a measure of air entering the engine. The best way is MAF sensing – ie actually measuring the air entering the engine. A Nissan RB26, being another I6 with individual throttles uses this. MAP + air temp is the next best, but falls over somewhat on an engine which uses individual throttles per port and you end up having to implement balance pipes to get a decent MAP reading.

TPS is the lest accurate way of measuring the air flow, but is the best we have on the Speed 6. This is why it has an adaptive mode (not just an on-the-fly lambda correction which is meant for tiny adjustments only).

So basically a rattly throttle butterfly will a) mess up the air actually entering the engine and b) mess up the reading the ECU gets, causing all manner of erratic behaviour – not just fuel but ignition timing too.

[m4tti]

How long do you estimate it would take for this issue to manifest in a sealed bearing? Do you have any links to case studies demonstrating how long it takes for the false brinelling to occur and under what conditions.

Edited by m4tti on Sunday 16th November 18:51

[Stunned Monkey]

As false brinelling is an effect of misuse, it's next to impossible to predict. However, bearing life is a function of temperature, load (both radial and axial), speed of rotation (and that's where this calculation would fall over), and bearing specifics like dynamic load rating.

A roller bearing will have a much higher load rating than a similarly sized ball bearing, so even under false brinelling conditions is likely to last much longer.

I'd guess signs of this effect would be a "click" that you'd feel through your right foot when you throttle up from idle.

I did some quick calcs based on typical idle vacuum and came up with a figure equivalent to 14kg standing on each throttle butterfly. Food for thought.

[m4tti]

Interesting, but aren't roller bearings utilised by a large number of throttle body manufacturers. What's the cost benefit of going the alternative route vs roller bearings.

And I'm guessing (from maths A level and statistics A level) that it would be difficult to calculate the wear as there will be huge variance in movement of the butterflies depending on how the cars are treated.

Conversely would different harmonics and vibration transmitted through the body not re distribute the lubricant within the bearing.

[Geoff Ashcroft]

What a great description, Monkey. I had mine bushed by TVR Power last winter and it solved a lot of issues including spitting and erratic idling (and I had already fitted TB gaskets to prevent air leaks). I couldn't feel the wear until all bodies were off the car and separated - then it hits you in the face. I didn't want bearings, as I understood they could also draw air if not properly sealed. Very pleased with the result so far.

[twinreal]

Andy did mine with sealed bearings and i was very pleased with the results, although i feared a kind of "butterfly flutter" resulting in hesitation when cruising. But nothing !
Adjusting the airflow was much easier and the engine runs very smooth now. Though i have to use pedal more sensitive now as throttle response is a treat - much more direct !
Maybe this is also because i fitted a set of new throttle springs. Would always do that again.

Thomas

[Stunned Monkey]

Hi All, thanks for the replies.

I am not aware of other manufacturers out there using roller bearings, but I admit the extent of my “research” stopped at Jenvey who I know and trust, and they use PTFE filled phosphor-bronze.

http://www.jenvey.co.uk/jenvey/why-jenvey-dynamics

This type of bearing is cheaper than a high quality, suitably high temperature sealed roller bearing, but we aren’t talking a fortune either way – probably under 20 squid. The real cost is in the accurate machining

I was able to garner the opinions of some colleagues at work and one ex-Rolls Royce engineer told me that jet engine internal guide vanes are always supported on plain bearings because of the small angles of movement and high vibrations.

Another potential issue with any rolling element sealed bearings is that the engine pulls a pretty hard vacuum which over time is likely to pull the grease out. I haven’t spent any time looking yet but if sealing is so vital - and it probably has more to do with dirt ingress than vacuum leaks - an axial lip seal (as opposed to radial like in a rolling bearing) would seem to me to be the obvious choice as it could be made to be self-energising AND act upon the end of the bush. Doesn’t look like Jenvey bother though.

I will probably source the bushes (and possible seals) myself and have a local engineering firm do the work. It ain't rocket surgery

Martin

[Sagi Badger]

Well, here's my tale;

I have 2 spare sets and 2 "running" sets, all in different forms.

Igus bearings in one throttle body, tried two types.... one that looked Oilite/hard plastic the other grey and quite tough but clearly lower duty. I forget the names, anyway couldn't get a seal even with a reduced tolerance hole in the throttle body and despite Igus running their smart car across Africa or somewhere with Igus bearings in everything except the crank it seemed, I wasn't convinced, I did actually discuss with technical as this was my first choice over Oilite bushes (PB).

Sealed ball bearings, 4 per body comprising 2 different sizes, so stepped counter bore in the body. Sealed onto shaft with retaining compound and press fit into the body, the seals overlap when different size bearings are beside each other, this was my brainy idea.... ummmhhh may fail yet. 1500 miles and so far so good.

What I am looking at changing is the adjustment set up, to make the tabs longer so the adjustment is finer. I want to do this as I am sure on hard vacuum the springs yield as the butterfly/plate gets pulled open and this action must be responsible for wear on the adjustment screw/tab.

Anyway each to their own but this is my take.

Whatever you do make sure the butterfly/plate is in the right, exact right, position when refitting as they will fit but be ever so slightly out off air tight seal fit when closed. Don't mix the parts and take time.


J

[Boosted LS1]

Basil Brush said:

Plenty of bushing options here if anyone's thinking of that route.

Great link, thanks.

[Stunned Monkey]

Sagi Badger said:

Igus bearings in one throttle body, tried two types.... one that looked Oilite/hard plastic the other grey and quite tough but clearly lower duty. I forget the names, anyway couldn't get a seal even with a reduced tolerance hole in the throttle body

Hmm, interesting. I haven't taken a close look but was thinking of using a V ring seal on a "top hat" type Oilite plus bush. Do you think there's enough room?

Sagi Badger said:

Sealed ball bearings, 4 per body comprising 2 different sizes, so stepped counter bore in the body. Sealed onto shaft with retaining compound and press fit into the body, the seals overlap when different size bearings are beside each other, this was my brainy idea.... ummmhhh may fail yet. 1500 miles and so far so good.

Strooth, there's a belt'n'braces approach!

Sagi Badger said:

I want to do this as I am sure on hard vacuum the springs yield as the butterfly/plate gets pulled open

This is very unlikely as this defeats the primary function of a butterfly valve - the relative pressure across it has no effect on the force required to move it (except for bearing load). How about changing the adjustment screws for a finer thread?

Sagi Badger said:

Whatever you do make sure the butterfly/plate is in the right, exact right, position when refitting as they will fit but be ever so slightly out off air tight seal fit when closed. Don't mix the parts and take time.

Noted, thanks!