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Discussion Starter #1
So this has come up often, our good friend Rao has mentioned it more than once, and the merits should be discussed.

The biggest reason we all retain indy TB's in our FI builds is because we have them. Other than that, they make plenum design complicated and expensive, they make enlarging difficult, there is even possibly some imbalance or delay in the way the individual plates move.

On an NA build, the indy TB's with velocity stack can not be argued with, they are simply the best and are only found on extremely high end cars....at least back in the late 90's.

But now, is keeping the indy TB's more of a novelty when going to FI? I'm about to design a custom intake manifold for myself, and I'm wondering if I'd get more benefit from a single TB. I've already roughly reverse engineered the stock manifold, so I have the geometry I need, but it is still a pain.

I'd love to hear any and all opinions.....even the 'you'll kill the soul of the car if you remove them' argument.

Thanks!
 

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this should get interesting ill be following this thread
 

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I'd love to hear any and all opinions.....even the 'you'll kill the soul of the car if you remove them' argument.

Thanks!
I am not sure improving the car is going to "kill its soul". I don't think the individual TB's are important per se, it was a way to improve engine performance from the factory.

You no more kill the soul by adding a single TB than by adding FI IMHO! Have at it!!:15:

Regards,
Jerry
 

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I absolutely would be interested in moving to a single TB on an FI build such as mine. I know that Osh at RMS did that with Basil's car, but I've never seen that car run (it's been under construction longer than yours and mine put together, Bob!)

--Peter
 

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Really depends on your desires and intended application(s) for the car I guess. For N/A engines, one of the benefits for decades of individual throttles was the precise control you have over variations in the engine's power output, especially minute changes needed to stay on track loaded up at 1.1g in 125mph turn 8 at Willow Springs :). The mass (i.e. volume) of air between the throttle plate and the intake valve is very small compared to the typical single TB or carb with a large volume intake manifold. Hence you get instant throttle response and, in some applications, very important control over engine torque output, i.e. you're brain is directly connected to the front-to-rear weight transfer and/or rear slip angle via your foot. Having modified two cars 30+ years ago that went from dual carbs on manifolds on one and K-jet on the other to sidedraft Webers which of course had individual very short runners from the each carb throat to the intake port, the most profound difference is that modulate-ability.

I think with FI upstream of the ITBs, a lot of this level of control might be muted. Not sure. For many who don't track their car or actually perhaps track the car but aren't interested in the very last bit of throttle control, it might not be something they would miss?
 
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I'm in for the educational benefit and the pot stirring.
 

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Discussion Starter #7
Seems as though people are afraid to touch this one.

Oh well.
 

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Afraid of what??

Individual throttle body is better - accept it :)
 

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Discussion Starter #9 (Edited)
I think people are afraid to speak against the indy tb's.

I think they are the best thing since aluminum for NA applications, just would like a discussion on FI applications.
 

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I think they are the best think since aluminum for NA applications, just would like a discussion on FI applications.
Thats about right. The advantage of ITBs is essentially nonexistent in a F/I application and thus beyond any performance benefits, the simplicity of a single TB system would be a benefit in it's on right in a F/I system. I think the reason we dont see more single TB conversions is the complexity of converting from ITB to single TB (I'd imagine its only slightly less complicated then retrofitting ITBs on a car without them) and people are hesitant to lose the "cool factor" of their cars.

I think if evolve or someone made a relatively plug and play kit, we'd see a lot more single TB S/Ced S62's running around. It does have a lot of benefits on a F/I car. I don't think anyone will argue against that
 

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I think people are afraid to speak against the indy tb's.

I think they are the best think since aluminum for NA applications, just would like a discussion on FI applications.
There is no question the stock ITB intake setup was never designed/optimized for FI therefore, there is room for improvement. The benefits of going single TB wouldn't be primarily from the single TB itself but from the intake. Ditch the ITBs and stock intake and you now have a clean slate for designing an intake optimized for FI. Certainly, BMW did with the turbo F10 M5.

Unfortunately, this is not the place to have this discussion. Don't believe me? Search "turbo".

You have easy access to machining tools so making a custom intake flanges shouldn't be a big deal for you. Fabricating an intake should be relatively easy too so I hope your next thread will be titled, "This is why you want a single TB"

btw, you need to update your thread :2:
 

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There is no question the stock ITB intake setup was never designed/optimized for FI therefore, there is room for improvement. The benefits of going single TB wouldn't be primarily from the single TB itself but from the intake. Ditch the ITBs and stock intake and you now have a clean slate for designing an intake optimized for FI. Certainly, BMW did with the turbo F10 M5.

Unfortunately, this is not the place to have this discussion. Don't believe me? Search "turbo".

You have easy access to machining tools so making a custom intake flanges shouldn't be a big deal for you. Fabricating an intake should be relatively easy too so I hope your next thread will be titled, "This is why you want a single TB"

btw, you need to update your thread :2:
+1

There's no question about it that the ITBs were designed for a naturally aspirated motor.

Get to work on designing a custom intake manifold / throttle body setup that's optimized for forced induction. Less talk, more fabrication! :2:
 

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Or just use one from a 540i :eek:
 

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Or just use one from a 540i :eek:

And use lesser parts on an M5? No thanks.

Whats next? You'll be telling me people will try and fit engines from a GM or something. hiha

On a more serious note, how would the ECU take to removing the ITB's. Would it not want to see the throttle actuator etc etc move with throttle input that will now be redundant? And will this in turn trigger a plethora of faults?

It seems as if the "easiest" part of a conversion would be the mecahnical alteration of a 540i manifold and TB or a custome plenum with 8 runners, the electronic side of it simply baffles me
 

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And use lesser parts on an M5? No thanks.

Whats next? You'll be telling me people will try and fit engines from a GM or something. hiha

On a more serious note, how would the ECU take to removing the ITB's. Would it not want to see the throttle actuator etc etc move with throttle input that will now be redundant? And will this in turn trigger a plethora of faults?

It seems as if the "easiest" part of a conversion would be the mecahnical alteration of a 540i manifold and TB or a custome plenum with 8 runners, the electronic side of it simply baffles me

I would just remove the ECU ;)

That is the trickiest part. On the other hand, the ECU doesn't know how many throttle bodies there are. I suspect that it would not be all that difficult to make the swap. The TPS and throttle actuation are likely similar or the same.
 

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If you can go single throttle body like a 540, does that mean you can also go to an eaton supercharger style setup?

yes, everything is possible with enough money, if I could do that for under 12k USD though....

oops, forgot to add the link with the info on the build:

http://www.bimmerboost.com/showthread.php?44507-Eaton-Supercharger-Kit-E39-540i/page8

Seems like a member there is offering to fabricate the adaptor needed to bolt on the supercharger.
 

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Discussion Starter #18
Excellent responses! Yes, the 540 manifold is basically a plug-n-play, however to optimize it for FI, I think using the bottom part may be what is most desired.

This proved what I hoped it would, there was no eureka thought on why it would be horrible to remove the TB's I had suspicions that it was a good idea, and had a few discussions offline with other members about it, but I couldn't get past the 'I really want to keep ITB's becasue they are really cool' thought process.

I think I may have a set of ITBs for sale soon.
 
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Excellent responses! Yes, the 540 manifold is basically a plug-n-play, however to optimize it for FI, I think using the bottom part may be what is most desired.

This proved what I hoped it would, there was no eureka thought on why it would be horrible to remove the TB's I had suspicions that it was a good idea, and had a few discussions offline with other members about it, but I couldn't get past the 'I really want to keep ITB's becasue they are really cool' thought process.

I think I may have a set of ITBs for sale soon.
It wouldn't be fun or easy from a manufacturing/design standpoint. You'd need to create some form of transfer runners that replace the throttle bodies. Unlike the M62 which has nothing underneath the manifold other than a coolant valley, the S62 has a lot of components underneath. I realize the throttle actuator would go away. But you will have to heavily modify the wiring, emission systems, and fuel system. The way fuel is injected into the system right now is also optimized for the most amount of atomization. Not sure if you wanted to retain that characteristic, but i'd imagine your flow angle would have a negative impact on the fuel system. Couple that with manipulating the system to accept that there is 1 throttle position sensor vs 2, scaling the sensor, then scaling the amount of air actually introduced, now were talking custom tune most likely. The icv would be easy, but the rest is a lot more work than it's worth. Just my opinion at least. That's why nobody has bothered, many of us could do it. But how many would realistically pursue it after the initial incurred cost? Everyone wants cool stuff on here, but very rarely does anyone every put their money where their mouth is these days.

-R
 

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Discussion Starter #20 (Edited)
I completely forgot about the fuel system aspect. I forgot they were part of TB casting. That will be fun reverse engineering......

The tuning issues are big, but if one is custom tuning, or going with an aftermarket ECU, it's really a non-issue.

Thanks for the input!!
 
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