Tuning 32mm throttle body on my 899!

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Tuning 32mm throttle body on my 899!

chrisb7777

Inline for a good time!
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Hi again!

So the next thing im looking to do with my cinq is put a 32mm throttle body in it, im hoping this will increase power and torque a little on my 899!

I have sourced a tb from my breakers yard however i have not purchased it yet as it doesnt have the spacer, and i cant find one on ebay or on the forum!

Can anyone help me out here?

I will be posting pictures of my progress to help anyone else who is doing this :)

Thanks!

Chris
 
Hi, mate. Did this mod whilst collecting bits for a 1242 conversion. Did'nt make much difference to honest. The problen stems from the fact there is a small hole as the inlet enters the cylender head, that is the restriction. It is alot smaller than the 30mm tb you have now.

1242 mod is 70% complete as of now.
 
Okay thanks the information, im not looking for a massive difference just a little more torque for hills etc! Is there anything else you can recommend to get the most out of it? I think ill do it anyway just for fun, not expensive :)

Thanks

Chris
 
I have just found one with the spacer for £35
Should be here by the weekend, and i have the weekend off!

Same here, will put a bigger engine in one day, but for now im hoping this will do.

Will keep you posted

Chris
 
Hi Chris, The 899 rocker cover has got an ali. spacer bolted onto it then there is a 3mm steel plate on top of that then the throttle body. You could get the spacer and plate bored out to 32mm to match the TB.

Steve.
 
Ye, i'm with rallycinq on this one. Depending on what condition your engine is in, the best way to get a little more poke is to make sure everything is kept tip top. I had a valve go on my previous 899, took the head off and ground in all the valve seats, pre tensioned all the hydraulic tappets and gave her a good service.

It ran lovely after that. Best option for getting the best out of an 899 is to get rid of those hydraulic followers alltogether, I am convinced they affect how far the valve opens and the difference between cylenders. Get the rocker gear from a uno 45 or 903 panda.

As for tweeking an 899, open up the cylender head hole [diamond shaped bit], use your 32mm tb with an induction kit, and remember gas as it leaves the engine is alot greater in volume as when it goes in, so a bit of exhaust work would be good as well. Dont bother with the exhaust manifold as this is sufficiently large for the 899 [suprisingly so]. Go from there back.

Do keep us posted as to your progress, it would be interesting to know how far you can push an 899. 100bhp? :p

p.s if you need info for sticking a 1242 in an 899 give me or ming a shout.
 
Any engine when properly assembled will generally go better than a stock run-in engine. If you have the time to improve on the manufacturers tolerances you can make quite a difference. My son's 1108 is a lot better than it should be after the engine was properly rebuilt giving not so much better peak power as a better spread of torque. In terms of acceleration it is noticeably better than it should be on paper.

The question of whether or not the 32mm throttle body will help comes down to what the head and manifold will flow in terms of gas volume and how smooth that gas flow is.

In raw terms you can simply use the cross-sectional area of the manifold port as a guide, if it drops below 32mm then the bigger throttle body is just a waste of time.

Where the ports split you need to compare the sum of all four ports - again if it drops below the magic figure, don't bother.

Just to throw a multitude of spanners in the works there is also the inlet ports on the head, shrouding of the ports by valves, valve lift, the radii of the bends in the manifold and the head ports, any restriction here can easily negate the benefits you might envisage.

Ultimately your torque depends on how much charge you can get into the cylinders at a given engine speed. The gas speed will increase but where there is a restriction the gas has to accelerate to maintain the volume flow - if that speed goes beyond a certain figure (approximately mach 1) the gas flow becomes choked. On Fiats it tends to be the inlet side of the head's gas flow that causes problems so most tuning work on the head goes into inlet ports, valve sizes, valve seats and combustion chamber shaping. The exhaust side works very well and if anything tends to be over specified.

Sorting out the effective valve lift can go a long, long way to a better improvement than the efforts on the throttle. Better still make sure everything is set right and then spend an hour or two on a rolling road to get the engine tweaked to perfection. The odds are the injector will need a bit of a clean, the fuel pressure will be off a little and your cam timing likewise slightly out. Get all of those right and the car will always feel much, much better.

(apologies for technical inaccuracies - it has been a very long time since I studied all this stuff)
 
Hi everyone!

Thanks for all the great info! I will be doing a lot more work in the future hopefully :) Im just looking at this as a bit of fun to see how much i can squeeze out of an 899 as no one has really tried much with them!

I recieved my throttle body yesturday and have fitted it! (photos will follow tonight)
My conclusion so far is, yes it is a bolt for bolt swap if you use the 30mm spacers!
All my work searching for a tb with the spacer was a waste of time as it is useless and wont fit! oh well!
I beleive the original spacer is the right size however, can anyone confirm this?
The only problem i am having is the metal plate that sits between the spacer and the tb, this is defineatly to small and i will be modifying this to the right size.

I am using the top part from the original as i know the injector works fine and its a lot cleaner :) this also avoids taking off the fuel lines!

Anyway i put it together with no mods to the spacers yet as i neeeded to use the car. Started up first time as always and idled a little hight tan normal but this soon resolved itself. Upon first driving i am finding the power is at much lower rpm and i dont need to open the throttle as far, however from about 3/4 throttle there is little or no difference except in sound! There is defineatly a little more power but not tons and it revs so much more freely!
I will be modifying the spacer/metal plate to the correct size as needed later and hopefully this will make a little more difference.

Would it be worth taking off some of the mount for the throttle plate to further increase airflow?

I will get some pics up asap!

Thanks for all your help

Chris
 
What you've described on the throttle opening is stereotypical of the throttle being too big.

You have a perceived increase in performance (more torque at lower throttle openings) but there is no difference in performance in the last 10-15% (bit of a guess based on your description).

What is happening is you are achieving peak air flow earlier on in the throttle opening progression, entirely as a result of having a larger throttle plate. Once you hit peak air flow the engine simply cannot ingest any more, the only difference is the amount of noise escaping.

The only time you may see more power (actually it is more torque but I don't want to start that old argument again) is at the top end of the rev range where the engine is working at its hardest to ingest air. At lower engine speeds the bigger throttle just doesn't make that much difference. The only way you'll find out if it is actually working is to do a comparison on a rolling road with both the original and the new throttle bodies.

If the peak airflow is being reached before the throttle is fully open (which it most definitely is) then what you have achieved is some scope for further development of the engine (such as a cam change or head porting). By itself the throttle body isn't going to make that much difference.

What everyone seems to keep forgetting is that Fiat have a remarkably efficient optimisation process (FIRE) that is used to work out the various sizes and tolerances on their engines. In some cases this means some parts are under specified as they don't believe will use the potential or they don't want you using the potential (typically for wear and longevity reasons) but by and large the whole engine has been optimised to work at something close to peak efficiency over a reasonably broad range of environmental conditions.

Changing anything on the engine quickly becomes a balancing act that results in a cascade of changes needed to keep things feeling sweet. This requires a holistic (never really thought I'd use that work in respect to engines) approach to development. From an engine tuners perspective it means deciding how much more torque is desired and then working out a series of small changes to achieve it.

For example getting an extra 5bhp out of your 899cc engine would go something along the lines of:

skimmed cylinder head
enlarged inlet valve
cam reprofile
enlarged throttle body
derestricted exhaust

The actual changes to each of those would be quite small to achieve the 5bhp but the cost of doing so would be unlikely to change to achieve a further 5bhp if performed at the same time - rendering a "simple" 5bhp hike uneconomic.

Please note this is an example, not a real set of changes, so please, no gripes or flames about inaccuracies. I'm just trying to prove a point.

In reality the complexity and cost of subsequent hikes in power increase roughly exponentially (the law of diminishing returns) so getting a worthwhile increase in performance out of a small engine can be both expensive and time consuming for very little reward.

Strangely it is Fiat's mid-range FIRE engines that seem to have the most tuning potential without resorting to forced induction. The cost of developing the 8v OHC engines is less than the 16v dohc engines despite the inherent potential of a 16v design. The 16v design is so heavily optimised that it is very hard to make "conventional" worthwhile improvements. Switch to forced induction and it is another matter as the real increase in performance does not rely on an increase in maximum revs or "eccentric" cam profiles (neither of which is particularly viable on the 16v design). The irony being that the playing field is merely flattened, not reversed - the 8v engine has pretty much the same potential with the added benefit of being able to rev higher although the poor 8v head will struggle at higher engine speeds.

Anyway, enough distraction, diversion and lecturing on my part
 
I beleive the original spacer is the right size however, can anyone confirm this?
The only problem i am having is the metal plate that sits between the spacer and the tb, this is defineatly to small and i will be modifying this to the right size.
Chris

I looked at the 899 engine which I have and the spacer and metal plate are 30.3mm dia.
Steve.
P.S Chris pm sent.

Rocker cover with ali. spacer
 

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When i intially was assembling the new tb i didnt have time to do any modifications to the spacers, so you are correct blu73, i was wasting the larger tb on smaller bore spacers. Therefore i was experiencing 'full throttle' at around 3/4 throttle. Although a small amount of power gain was marginal. Thank you jimbro1000 for your your comments, i think if i ever get round to further mods on this engine i think i will have swapped the engine for a 1.1/1.2 or larger. I have a good go kart frame rusting in the garage for one day ;)

To continue on other work i have done since i last posted. I took the metal plate that sits between the spacer and body and filed it down so it was the same size as the original spacer, which is 30.3mm as sparky 5 has pointed out (pm sent btw :) )

Took it out for another spin and the power gain are very noticable now, i find accelaration a lot quicker, the torque band has moved a little but i havnt lost any yet. Power at the top end is has improved a little, but between 3 and 5k the has certainly been a boost!

Here are some photos i took:

Before everything was taken apart




New 32mm on the left and 30mm of the right, you can see quite a difference!

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DSC_0273.jpg


This is the metal plate i mentiond that sits on top of the spacer, i have filed down the inside to match the spacer size now

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The original spacer that came with the 32mm tb

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Very soon i hope to get the spacer and plate properly bored out to achieve the tb maximum potential!

Thanks for all your comments and help so far

Chris
 
So iv done about 1000 miles since I swapped over the tb and everything has been fine, until now!!!
I was stopped at some traffic lights and the idle suddenly started raising up and then dropped, then again.
I kept driving till I got home, when I stopped the idle was hunting real bad between 1k to 2k. If I leave it to do that for around 15secs the idle raises to a steady 5k! This only stops if I tap the throttle, where it return the to initial hunting and so on...
I have also noticed when driving if I take my foot off the accelarator it keeps accelerating for a second like there is a delay!
I unpluged the IAC to see if it would stop the hunting but it makes no difference at all!
It does it at all tempretures

Any ideas?

Chris
 
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