Member
Big Bore Throttle bodies, the truth, and any better alternative?
hey guys. after looking at throttle body for some time now and making various measurements I have come to a conclusion. Why doesn't a company out there actually develop a Larger throttle body instead of machining them 3-4mm and calling it "big bore". Seems like there would be alot of power to be make b/c the throttle body opening is so small
Stock HFM is 3.0 inches opening
Euro HFM is a whopping 3.5inches
Stock throttle body is only 2.7-2.75 inches inner diameter. even the OUTER diameter is only 2.9 inches. that seems like such a huge bottle neck. If someone made a 3.0 throttle body with custom elbow (which i'm trying to develope) and matched them together seems like powergains would be hell of alot better than the 3-5HP you get from big bore TB now.
Is there anyway to retrofit a TB from a bigger bimmer motor (maybe 5 series or 7 series). has anybody thought about this at all?
This probably really only applied to NA, FI it doesnt really matter. anyways what yall think? any comments or suggestions or etc would be nice.
My 2 cents
Member
[QUOTE=SupaBimma]hey guys. after looking at throttle body for some time now and making various measurements I have come to a conclusion. Why doesn't a company out there actually develop a Larger throttle body instead of machining them 3-4mm and calling it "big bore". Seems like there would be alot of power to be make b/c the throttle body opening is so small
Stock HFM is 3.0 inches opening
Euro HFM is a whopping 3.5inches
Stock throttle body is only 2.7-2.75 inches inner diameter. even the OUTER diameter is only 2.9 inches. that seems like such a huge bottle neck. If someone made a 3.0 throttle body with custom elbow (which i'm trying to develope) and matched them together seems like powergains would be hell of alot better than the 3-5HP you get from big bore TB now.
Is there anyway to retrofit a TB from a bigger bimmer motor (maybe 5 series or 7 series). has anybody thought about this at all?
This probably really only applied to NA, FI it doesnt really matter. anyways what yall think? any comments or suggestions or etc would be nice.
My 2 cents[/QUOTE
Makes sense to me
Red Assed Baboon
Although I do not know for sure but I would say that it has a lot to do with the intake also. What size is the hole in it? How easy would it be to custom machine the intake and say "build" a whole new throttle body. Like say an aftermarket company does? Like BBK or Edlebrock? I am not sure what we would run in to, because it may not be that easy. The TB mounting holes may be too close to actually make a 3.5" or even a 3" TB then we would have to re engineer a whole new intake. I would be willing to fund a prototype just to see real world gains, then if we get say 10 to 20 hp out of it, how much would we be willing to pay for a whole intake and TB setup? Many, many questions but I will have some answers come friday when my new BBTB comes in.
I have recently ordered one from Riot Racing, but when I get my old one off I am planning on checking out the situation with this myself. It would be ideal to have a 3.5" TB seeing as we pay alot of money to do the same with the rest of the intake.
Last edited by rab986; 07-21-2004 at 10:12 AM.
Understeer FDK, UUC Underdrive Pulleys, UUC Red TME, UUC Comp EVO3 SSK, UUC DSSR, UUC Clutch Stop, UUC Stage2 Flywheel w/M5 clutch, Supersprint headers, AA Exhaust, JC CAI, Euro MAF, JC software, Riot Racings Big Bore Throttle Body, Strong-Strut Competition Strut Tower Brace, TMS RTAB's & shims, AA DSB, AA RCCA's, Ground Control Track Plus Coilovers, GC Street Camber Plates, GC Tubular front and rear sway bars, 3.46diff w/40% lockup, Schroth Harnesses, 17x7.5" Lightweights, Toyo 235x40's. Cobra Imola II Seats, Momo Jet Carbon Fiber Wheel, SSR Comp wheels, IOport Racing 8 point Cage, Mpact Motorsports CF Gauge kit,
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the reason is b/c i have EUro HFM and i feel the stock TB is such a bottle neck. i believe the bolts are far enough to make an opening 3.0". 3.5 would probably require whole new intake. Eventually i may try and develope some crazy ass intake, but intill then baby steps
Red Assed Baboon
yeah, I took a look at it this morning and 3.5" may be a stretch. The TB looks pretty simple compared to others I have messed with (GM), so it may not be to bad of a project.
Understeer FDK, UUC Underdrive Pulleys, UUC Red TME, UUC Comp EVO3 SSK, UUC DSSR, UUC Clutch Stop, UUC Stage2 Flywheel w/M5 clutch, Supersprint headers, AA Exhaust, JC CAI, Euro MAF, JC software, Riot Racings Big Bore Throttle Body, Strong-Strut Competition Strut Tower Brace, TMS RTAB's & shims, AA DSB, AA RCCA's, Ground Control Track Plus Coilovers, GC Street Camber Plates, GC Tubular front and rear sway bars, 3.46diff w/40% lockup, Schroth Harnesses, 17x7.5" Lightweights, Toyo 235x40's. Cobra Imola II Seats, Momo Jet Carbon Fiber Wheel, SSR Comp wheels, IOport Racing 8 point Cage, Mpact Motorsports CF Gauge kit,
Member
ya 3.5 not possible but 3.0 would still yeild great results i think b/c that would be something like 8-10mm bigger compared to just a 3-4mm bigger "big bore" throttle body
Member
hey guys, I will be looking into this and looking at every possible BMW TB and see what measure what the largest bore is for the same bolt pattern. i hope i find at least one larger match. i'll keep yall updated.
Cone Killer
Considering that adding even 3-4mm yields no power whatsoever, I highly doubt that the throttle body is an issue.
'03 911 Turbo 6MT fun car
'18 Toyota Land Cruiser Daily driver/Ski Machine/Off Roader
'15 Cayenne Diesel Wife's DD
'17 KTM 690 "Adv" 2 wheeled Adventurer
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it does add power but only on M3's with euro HFM and larger intakes, the first bottle neck is HFM, the next one is the TB. TB only makes a difference when you have all the other performance components inplace. you are rigth now 3-4mm (most normaly Big bored TBs) makes 3-5 crank HP at most, thats why i want to find an alternative thats much more substantial for much less price. i'll keep yall updated.
Member
I dont think I have ever seen anyone post a dyno graph showing any gains from just adding a bigger TB, ever. 3-5 HP is well within the %error/difference that shows up between dyno runs, so it will be hard to prove anything even if you do manage to find somthing that fits. Hey if you really want to do somthing special, fab. up a throttle body with a sliding gate opening (i forget the real name for it) instead of the butterfly.
-Peter
Current toy: none
Past cars: 88 M3, 99 M3 x2, 04 M3, 91 NSX, 06 S2000, 01 911TT, 06 Exige, 00 NSX, 04 GT3
Member
your 95 does not have AST, but for those of us who do have it, that appears to be the biggest bottleneck right there.
97 Estoril/Black M3/4/5
"Although we've experienced an M3 sedan with an automatic, our test car came fitted as God intended, with a 5-speed manual ..."
Road & Track May 1997, testing the M3 Sedan
Member
When we obd2 guys remove it, we pick up a whopping 1 hp maybe. Its not becuase obd2 sucks like I am sure everyones thinking, its because we are much more limited by the efficiency of our cams, our head's design and other things like that.Originally Posted by M3 Pete
-Peter
Current toy: none
Past cars: 88 M3, 99 M3 x2, 04 M3, 91 NSX, 06 S2000, 01 911TT, 06 Exige, 00 NSX, 04 GT3
Resident Podiatrist
It doesn't add power(2-3HP isn't "added power" in my book), yes, but the response is much crisper, especially on the beltway. The car instantly picks up throttle response when you step on the gas slightly.
Most will disagree for the money, but it helps for certain situations(e.g. passing a slower car easier instead of downshifting). It's a bit pricy, but it helps and is definitely noticeable...
For the thread starter, I did a writeup/impressions thread months ago, check it out, it may be helpful. I think it was called "Review/Impressions: Dinan Bored TB" or something to that extent. Good Luck...
Member
I'd have to agree with the posts above.
If the OBD2 guys are removing the trac. control throttle body which is tiny compared to the main throttle body and only picking up 1-2hp, then there is not going to be gains by making the main throttle body larger.
You have to remember that bigger isn't always better.
The only way to tell is to do some flow measurments. I highly doubt you would find that the TB is a huge restriction.
Then again, go ahead and test it. But, get before/after dyno's to prove the test.
Team Old Guy Racing
You've got bottlenecks all along the air pathway leading into the cylinders. You're best bet is to increase the airflow all along the system. You've started with the intake and the HFM, so that's good. A TB change from 64mm to 68mm will give you a 13% increase in airflow thru the TB, but then you've got the intake manifold and head. :eek
If you change to the better flowing m50 head and then add cams, you've pretty much maximized your airflow into the cylinders. That's the right way to get the most out of the TB, but I say "every little bit helps"
///Max
Member
How about a tbody from a 840,540,M5???
I've never checked, but wouldnt they be similar
in in design??
jay
infamousm3
Team Old Guy Racing
Sorry, don't know that answer for sure...
Last edited by Max M3; 08-08-2004 at 06:31 PM.
///Max
Member
I just took a quick peak into a Summit catalog, and it looks like Mustangs use a 4 bolt pattern for their TB, just like the E36. Now, the question is if the bolt pattern is the same size. I would doubt it, but it might be worth checking into.
Both Edelbrock and BBK TB's are listed in Summit, up to 75mm (~3inches). Not to mention, under $200.
Member
hey spencer, ya i looked into that, i looked at Jegs catalogue and they have ton of sizes ranging from 62mm-80mm LSI throtttle body, and they bolt patters are very similar but again it comes down all to the measurements. they are pretty cheap though. I will measure the intake manifold exactly in mm to make sure i get just slightly smaller than the opening itself. but if 75-80mm throttle body is possible that seems like a huge increase airflow in my opinion.
Regarding bottlenecks. A bottle neck is where diameter is larger, then gets really small, then opens up again, there for "bottle neck". diameter gettting smaller and smaller is good, thats more a Velocity stack then a bottle neck. you want it to get smaller and smaller as it goes along, but not big>small>big, that is not good. the stock TB is fine for stock HFM, so even if you change TB's from OBD2 to OBD1 you won't see much of a gain b/c no extra air is coming in. But if you have a Euro HFM, theres a substantial more amount of air coming in so the gains would be slightly more. again we are not talking 20HP or something, just a few HP seperating the two but again every little body counts in my opinion.
Honestly nobody knows b/c its never been done, yes few have done "big bore" but thats such a small change in diameter in comparison. anyways i will keep yall updated.
Member
The stock TB is 64mm right? Whats the bolt pattern on the stock TB? Will a BBK or Edelbrock TB attach without throwing a code?
Member
I'm new to my E36 M3 but not new to fooling with cars. Ford TB sensors produce a 5V signal (+/- about 0.2V) at WOT, and, since they are OBDII cars, so should the BMW Tbody sensor. So, if you wanted to slap one on the computer should not know any difference. Lots of tbodies out there and some of the eariler 89-93 Mustang units look close in fit if my memory serves.
Member
i believe 64mm is correct stock size. realistcally i don't see there being more than a 75mm TB b/c i think intake manifold opening is 75mm roughly (not sure exactly, need to measure). alot of the american throttle body pictures in the catalogue are VERY similar in look, but it all depends on the exact measurements from bolt centers vertically and horizontally to know for sure.
Member
While I dont have a great mental image of what the area looks like, wouldnt it be rather simple to fabricate an adaptor plate for one of these 'american' throttle bodies you are refferring to? I cant imagine one thats going to ever bolt right up...that would just be too easy. All it would take is some measureing, 30 minutes in a machine shop, and the correct throttle body in terms of electrical wiring.
-Peter
Current toy: none
Past cars: 88 M3, 99 M3 x2, 04 M3, 91 NSX, 06 S2000, 01 911TT, 06 Exige, 00 NSX, 04 GT3
Duder
I'm loving this thread right here, you guys are awesome, i think this is gonna work out nicely,, at the rate you guys are going i know one of you will figure out a "big bore" TB sooner or later.
M driver, RSV4 Rider, Powerstroke roller
Member
OBD1 throttle bodies have no electrical wiring so alll that matters is it if will bolt up and fit pretty much.
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