18psi

iTrader: (76)

Have you personally tuned a small engine with a huge throttle body? Let's see the logs

RalliartRsX

The AEM drift Scion uses a 66mm throttle body to make 1000 HP on a 2.7 4 cylinder because "better throttle control on the smaller throttle body vs the big 90mm with no loss of power"

Yeah, big throttle on a little engine is futile.....especially considering you can make 500+ WHP on a 65mm throttle body all day while retaining all granularity in terms of throttle adjustment and control (regardless of DBW or cable operated).

So yeah.....I am more inclined to believe the folks who have gone through it. Also, I did the same thing on a sub 400 WHP 4 cylinder (90mm vs 65mm). Never again........

ITOzann

Here is another option that is widely popular in Australia.

Bosch Motorsport DBW with many bore diameter options

RalliartRsX

Ever thought about the 350/370Z DBW throttle body??

Reverant

iTrader: (10)

This is not a matter of whether the ECU is powerful or not. If opening the throttle plate 0.1% yields a 150rpm increase, you can't control the idle well on this large of a throttle body.

ITOzann

This may be true for most instance where TPS is activated between 0% to 5%. The throttle position translation tables can be overwritten and some extra compensation may take place. A good initial calibration file along with fine parameter tuning alleviates most of the problems encounter with a DBW setup. FYI, there are many high horsepower builds running Motec systems with stock-like driveability characteristics.

shlammed

iTrader: (8)

you can force 1000hp through a 2.5" exhaust too... doesn't mean you don't get the efficiencies of a larger system.
Granularity in a DBW is relevant because it is what you tune it to be.

RalliartRsX

You have missed on single key fact; There was no loss of power going to a smaller TB when running a 2.7 liter 900HP 4 cylinder. There WOULD be significant efficiency and pumping losses by trying to shove 1000HP worth of hot expanding highly energized exhaust gas volume through a 2.5" pipe. I wouldn't necessarily equate the two in your analogy .............

With that said; why would you make your job harder and waste throttle plate resolution?? By going to a larger TB, you essentially would only need to open the plate 25%-35% to flow enough air needed for sub 500WHP. Why even bother wasting your time on something that is physically larger and not necessarily needed??. There is actually a physical limitation via plate size.

Don't take offense, but I would be more inclined to emulate the Papdakis drift team with several decades of experience. Also, I have gone down that road, and never again.

Have you personally tried to a tune a small displacement 4 cylinder turbo car on a 90 or 80mm throttle body be it DBW or cable?? MototIQ did a write up recently on a 5.0 Coyote Engine with a much too large TB and even with DBW, it was a bitch. You should go check it out for reference

18psi

iTrader: (76)

He just likes to talk.

RalliartRsX

It sure seems that way. From what I have seen, anything larger than a 70mm TB on any turbo 4 cylinder is entirely unnecessary, DBW or not. Physics and common sense do come into play at some point lol.

TurboTim

iTrader: (9)

apples/oranges, even still this discussion reminded me of this recent clever solution for driveability with a 'large' throttle body.

RalliartRsX

LOL! Four 150 feet diameter inlets are always better than a punny 70 mm

P.S Short wheel base big block?? I like my coffin with blower sticking out the top

TurboTim

iTrader: (9)

Yeah, kinda funny when your 'small' street throttle body is 105mm.

only 520ci.

shlammed

iTrader: (8)

no loss of power? I would wager that there is in fact losses. they also use a box plenum intake manifold... im sure there are losses there too but they spent a bunch of time in other places. intake efficiency losses and exhaust efficiency losses are apple and oranges but there is no reason a good ecu and a large throttle body cant work out. step out of the Miata/import world for a minute and see what people are doing - its enlightening.

18psi

iTrader: (76)

step out of the clueless bench racer world and realize the only cars using giant throttle bodies are PD supercharger cars...where they actually do help and improve power.

OP,
if you want any of this cleaned up just let me know.

RalliartRsX

You do realize Papadakis' 2.7 TOYOTA 2.7 liter EFR 9174 powered vehicle is not Miata world right?? You do realize my username as well right?? You do realize I mentioned the MotoIQ article in regards to the Coyote 5.0 V8 and their issue with a 102mm DBW throttle body right?? You also realize I do not own a Miata right?? You do realize I have referenced several distinct engines way removed from the Miata world right?? You also realize Turbo Tom posted a blower a top a IM manifold with a large TB right beneath right??

The irony is not lost on your post

Again the question; have you tested a much larger than standard and (in this specific case a 90MM DBW/cable) on a 2 liter turbo 4 cylinder with a small frame turbo??

If Papadakis is building a 900HP 2.7 liter 4 cylinder and has demonstrated there is no HP loss by stepping down to a 66mm throttle body (he has a dyno video mind you), I am going to believe him over someone who is equating pumping 1000HP worth of hot energized expanding exhaust volume down a 2.5" exhaust to ~40PSi of Nitrous air charge through a 66mm throttle body in a ~2.7-3 liter plenum

IJS......

ITOzann

I am good and open to anyone's input about any topic. After all, we don't have trade motorsports engineers in here.

Savington

iTrader: (31)

You'd lose that wager. I tuned a Rotrex car last year which, unbeknownst to me, was only opening the 70mm aftermarket B-series throttle to around 80% TPS. We were hunting for a restriction, since the car was down on power from what we had been expecting, and we assumed that we had found it. Nope. Owner manually actuated the TB to hold it fully open for a pull, and we saw zero gains at ~270whp.

There are physical reasons why large throttle bodies simply cannot be made to have the same driveability as small throttle bodies, 521ci water-jacketed funny car engines with 105mm throttle bodies aside.

Your flippant dismissal of the "Miata/import world" belies an inherent lack of experience that is reflected in your posts.

Savington

iTrader: (31)

Sure we do. I've seen PhD candidates, senior-level engineers at Mazda, racing engineers, national champions, shock engineers, and all sorts of other industry professionals quietly add their $0.02 in various places on this forum.

You should never assume that all opinions are equal, ever. Some people know more about certain topics than other people, and their opinions should be weighted as such.

RalliartRsX

Meh. I havent been around long enough or have much stock in a forum or the internet to care enough have someone's post deleted lol. Let ignorant people be. They will eventually learn.........or they don't

Afterall, this IS the internet. Real world results from the proper engineering minds are rarely posted on forums.........and rightly so as shlammed is a perfect example of why I wouldn't either lol.

I will just relegate myself back to lurking and building my non Miata

P.S The irony of mentioning a box plenum and not realizing that it actually works fairly well on a K series lol. Didn't Andy post proper results from his box style plenum on his KMIata?? Again, ignorance and irony not lost on his post.....