IRTB goodies

Engine work, Tranmissions, LSD's, Diff swaps, etc
User avatar
Ken P
Stage 4+
Posts: 10051
Joined: Tue Dec 04, 2007 12:14 pm
Car(s): 2014 NC GT
Car(s): 2013 Fiat 500 Abarth
Location: Jungles of Antartica

Re: IRTB goodies

Postby Ken P » Mon Mar 24, 2008 4:58 pm

agreed. i think having ITBs is like being married to a really high maintenance woman, constant attention and money needed. some people like that stuff. i know if i was retired with a million bucks and lots of time on my hands, id do it. mainly to keep myself busy.
Member of the Brake Fade Society.

Keep up with RetroModern's latest products
Instagram: @retromodernusa
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Wed Mar 26, 2008 1:22 pm

Popstoy wrote:Can I butt in, while I've never had IRTB's, I have had many multible carburated on individual runners, and they're a pain in the ass, they require constant balancing, particularly if you require maximum performance, they won't idle worth a damn, even worse with a built motor, makes the engine very finicky to atmospheric conditions, like temp, humidity, altitude. On a computer controled engine like the Miata, where the a/f ratio is controled by sensors, and adjusted after the fact by the 02 sensor, which is an average of all 4 cyclinders, I sure wouldn't want different cyclinders running at different a/f ratio's, and that's what you'd get unless they're kept in perfect balance. Then you've got the problem of how to filter the incoming air. Sure you could put individual filters on them, or build something, so that they all draw air from a common soarse, like a huge airbox, as used on most motorcycles. You know, there are many ways to improve throttle responce, and power, dollar for dollar, irtb's have to be one of the more exspensive, least productive, and high maintance way's to go. Bob


a properly set-up itb won't need constant adjustment, and assumiing you're running a good standalone engine management system you shouldn't have to worry too much about temp, humidity. it's unfair to compare carbs to efi itb's.
Popstoy

Re: IRTB goodies

Postby Popstoy » Wed Mar 26, 2008 7:28 pm

twmboy, Obviously, you don't understand how irtb's work. First, they get out of balance just a easy as any multiple carburated, individual runner set-up's do, both are mechanicaly adjusted to put them in syn. Carb's have one advantage over irtb's, they're jetted instead of injected, meaning the a/f ratio is fixed, only dependent on the amount of air passing thru each one of them. On a irtb system, only one tb has sensors for the computer to read and adjust for, the computer assumes the other three are passing the same amount of air, and if they're not in syn, each passing the exact same amount of air, the a/f ratio can easily be different, as all the injector's will be putting out the same amount of fuel to each cyclinder, but the amount of air is different. Secondly, if you think the air being drawn into each irtb is the same, your mistaken. The only way to garrantee that, would be to have one common soarse for the incoming air, like one big air box, and I'm not talking about just under the hood, as the pressures and temps can vary dramaticly, depending where under the hood it's sucked from, and usually is, regardless of the airhorns being only inches apart. The two advantages of less restriction for more airflow, and a smaller plentum area for better throttle responce, can easily be negiated by being out of syn and incorrect a/f ratio's, regardless of the state of tune or the capabilities of the computer. Bob
User avatar
loanpro
Stage 3
Posts: 1987
Joined: Thu Jan 03, 2008 3:35 pm
Car(s): 04 Impreza Sti
Car(s): 05 Nissan Titan
Car(s): 92 MBZ 400E
Location: Bay Area
Contact:

Re: IRTB goodies

Postby loanpro » Wed Mar 26, 2008 7:50 pm

Well, speaking from experience...I've had twin carbs on my AE86 and it's a pita to tune...always with the use of a syncronizer, air-jet, main jet, venturis has to match...then after getting it tuned right (so you think), it's only good for so long. As for my ITB's, the same case in the beginning...but once it was tuned, I never had to touch it again unless I added another mod, like cams or higher octane gas.. But my tuner took a very long time tuning the darn thing..on the dyno and on the street...at idle, partial throttle, Wot, you name it, he fine tuned it... I guess depends on what ecu you're using, you can easily get maximum potential in either one...

On the other hand, the same power and probably even throttle response can be achieved using a single throttlebody...avoiding the added cost and trouble of fine tuning.

But, you can't put a price on the Growl and "Poser" points of having ITB's :nutkick:

Bottomline, if you can afford it, go for it!
Irvin Sevilla, Finally employed since 11/1/12, Lost it again, 4/14/14
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Fri Mar 28, 2008 11:57 pm

As I stated before, carbs ( while similar in regards to individual runners ), can not be compared to efi itb's. Carbs, having more moving parts in regards to fuel atomization, are more sensitive to altitude and humidity change. a "simple" solution for efi itb's is a maf based fuel map ( bmw has proven this through their M line of sports cars ). if you're running an alpha N (tps/rpm based fuel enrichment) you're more likely to suffer from the same down falls as carbs. while I respect your first hand knowledge of carbs popstoy, I have more experience with itb's.

other than the original syncing through the factory ( the itb's were heated to 300*F and then synced ), the dvs honda drag team required zero re-syncing throughout the season. would this car work the same if it were operating in colorado? obviously no because of the difference in atmospheric pressure.

other than race applications, personally I don't think itb's are a practical application. for what it's worth, the linkage on the miata kit below is the same linkage used on the k20 dvs honda. the plates are synced from the factory ( as I stated before ) and the single linkage system has proven to be more reliable than a dcoe style itb linkage.

Image


lastly, a well put together ems system such as motec or pectel can handle the various sensor inputs for the different runners (again, a trick used by the dvs honda drag team). you're knowledge of carbs has skewed your view of efi itb's.
User avatar
LastManStanding
Stage 3
Posts: 1522
Joined: Sat Jan 05, 2008 2:30 am
Car(s): Boat(s)
Car(s): Torch(es)
Car(s): Egg(s)
Location: Location: Location

Re: IRTB goodies

Postby LastManStanding » Sat Mar 29, 2008 12:49 am

twmboy wrote:while I respect your first hand knowledge of carbs popstoy, I have more experience with itb's.

I think pops point was that real tuning would simply cost too much. Even if they are all flow rated correctly and don't suffer from drifting, differences in engine bay pressure and heat will cause different conditions in each cylinder, especially in longitudinal engine as there is a big difference between the front and back of the engine bay. The only way to account for this is to tune each cylinder, which means you need a wide band in each exhaust port. That's a lot of money right there.

My gripe with itb's is that they get rid of one of the most impressively engineered areas of the car; the intake manifold. As I stated earlier in this thread, manifolds now days are variable and are able to increase torque across the entire band. It is a highly designed and well calculated piece of equipment and getting rid of it just because some race cars use itb's is just silly. Since I like numbers let me throw some out there:

If you were to get a set of itbs for the miata and tune the runner length give the largest boost in torque at 7500rpm you would need a runner length of 11inches. The ones you posted in that picture look to be half that length. The best approach would to tune them for around 5500 since that is where the torque curve seems to be strongest and would provide a boost both above and below that point; that gives us a runner length of 15inches. About 3 times longer that the one you posted. As you can see, aftermarket itb set ups really aren't tuned or tested for optimum performance. They probably give a slight performance gain over stock, but that's mainly due to the accordion tubing and stock filters. A good manifold with a well made air ducts would net the same result if not more.
Lunch Control - in which you hold down the brake, floor the gas, then the revs drop to 1k, clutch engages and it takes you to a restaurant you've never been to before
"Look at that fat girl; is she wearing a flag? It looks like she sowed two flags together and decided to wear them."
User avatar
Ken P
Stage 4+
Posts: 10051
Joined: Tue Dec 04, 2007 12:14 pm
Car(s): 2014 NC GT
Car(s): 2013 Fiat 500 Abarth
Location: Jungles of Antartica

Re: IRTB goodies

Postby Ken P » Sat Mar 29, 2008 1:36 am

holy sheeet i think i just wet myself.
Member of the Brake Fade Society.

Keep up with RetroModern's latest products
Instagram: @retromodernusa
User avatar
loanpro
Stage 3
Posts: 1987
Joined: Thu Jan 03, 2008 3:35 pm
Car(s): 04 Impreza Sti
Car(s): 05 Nissan Titan
Car(s): 92 MBZ 400E
Location: Bay Area
Contact:

Re: IRTB goodies

Postby loanpro » Sat Mar 29, 2008 1:46 am

genghis ken wrote:holy sheeet i think i just wet myself.


Nope, that was me..Get your hands off my pants!~ :nutkick:
Irvin Sevilla, Finally employed since 11/1/12, Lost it again, 4/14/14
Popstoy

Re: IRTB goodies

Postby Popstoy » Sat Mar 29, 2008 1:08 pm

While I have too agree, those things are extremely sexy, and pure simplicity in design, their application doesn't lend itself very well to anything other than wide open throttle, racing applications, which is the exact application Honda Drag racing is using them for. There are very good reasons why a pure race car isn't fun to drive on the street, this is just one of the examples of why. Bob
User avatar
Ken P
Stage 4+
Posts: 10051
Joined: Tue Dec 04, 2007 12:14 pm
Car(s): 2014 NC GT
Car(s): 2013 Fiat 500 Abarth
Location: Jungles of Antartica

Re: IRTB goodies

Postby Ken P » Sat Mar 29, 2008 1:40 pm

pops, i have to disagree with you on that statement. Irvin's civic was very docile and streetable IMO.
Member of the Brake Fade Society.

Keep up with RetroModern's latest products
Instagram: @retromodernusa
Popstoy

Re: IRTB goodies

Postby Popstoy » Sat Mar 29, 2008 8:30 pm

Ken, I told you, you wouldn't like the koni/GC kit's, but you didn't lisson to that either. Bob
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Sat Mar 29, 2008 9:44 pm

for shits and giggles....

Image

Image

Image
Popstoy

Re: IRTB goodies

Postby Popstoy » Sun Mar 30, 2008 1:40 am

How much for all that sex?
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Sun Mar 30, 2008 11:52 am

retail is $2349 with injectors and everything you see in the pics. everything minus the actual casting (twm does their own molds) and anodizing is done in house at twm (casting and anodizing is done only thirty miles away in ventura).
User avatar
Ken P
Stage 4+
Posts: 10051
Joined: Tue Dec 04, 2007 12:14 pm
Car(s): 2014 NC GT
Car(s): 2013 Fiat 500 Abarth
Location: Jungles of Antartica

Re: IRTB goodies

Postby Ken P » Mon Mar 31, 2008 1:12 am

Popstoy wrote:Ken, I told you, you wouldn't like the koni/GC kit's, but you didn't lisson to that either. Bob

not true. i actually like them alot. its just that i feel that ive outgrown them. good beginner setup though :woot:
Member of the Brake Fade Society.

Keep up with RetroModern's latest products
Instagram: @retromodernusa
Popstoy

Re: IRTB goodies

Postby Popstoy » Mon Mar 31, 2008 10:41 am

$2349, with injectors, but without the manifold, and without the management needed? Such a deal, for what, maybe 10-15 hp, a little better throttle responce, even if you can get and keep them tuned correctly. All that sex, and very little foreplay. Bob
User avatar
loanpro
Stage 3
Posts: 1987
Joined: Thu Jan 03, 2008 3:35 pm
Car(s): 04 Impreza Sti
Car(s): 05 Nissan Titan
Car(s): 92 MBZ 400E
Location: Bay Area
Contact:

Re: IRTB goodies

Postby loanpro » Mon Mar 31, 2008 11:26 am

Yep, all that money for that bulge underpants, I mean underhood ;) Why so expensive? The B-series TWM all inclusive is only $1500 shipped...
Irvin Sevilla, Finally employed since 11/1/12, Lost it again, 4/14/14
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Mon Mar 31, 2008 12:29 pm

Popstoy wrote:$2349, with injectors, but without the manifold, and without the management needed? Such a deal, for what, maybe 10-15 hp, a little better throttle responce, even if you can get and keep them tuned correctly. All that sex, and very little foreplay. Bob


what are you talking about? that IS the manifold. it's not some two piece dcoe style setup like OER. as for the engine management, if you're too cheap for it, then itb's aren't for you.
User avatar
Papa Smurf
Site Admin
Posts: 10629
Joined: Wed Nov 28, 2007 7:21 pm
Car(s): '93 'Papa Smurf'
Car(s): '92 Miata 'Silviata'
Car(s): '03 Porsche BoxsterS
Location: Taipei, Taiwan
Contact:

Re: IRTB goodies

Postby Papa Smurf » Mon Mar 31, 2008 1:02 pm

i equate paying up the ass for nice 10-15hp increase ITB's the same as owning a Bugati Veyron in a US city.
NCR window decals! $4
Image
Do you know someone who wants to buy or sell a house? I'll buy a $500 car part, when we close escrow as a "thank you" to you for the introduction.
User avatar
Ken P
Stage 4+
Posts: 10051
Joined: Tue Dec 04, 2007 12:14 pm
Car(s): 2014 NC GT
Car(s): 2013 Fiat 500 Abarth
Location: Jungles of Antartica

Re: IRTB goodies

Postby Ken P » Mon Mar 31, 2008 1:29 pm

i equate $2400 ITBs with 10-15hp increase to being the only one banging the office hottie. its a nice previlege that not everyone has.
Member of the Brake Fade Society.

Keep up with RetroModern's latest products
Instagram: @retromodernusa
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Mon Mar 31, 2008 1:55 pm

loanpro wrote:Yep, all that money for that bulge underpants, I mean underhood ;) Why so expensive? The B-series TWM all inclusive is only $1500 shipped...


the B series TWM kit is not all inclusive. it includes all the parts above ( ie no ems and no injectors ). if you took away the injectors from the miata kit it would be about $2000. also the reason for the mark up is quantity made/sold per year. TWM sells 10 times ( or more ) b series kits then miata kits a year, so retailers discount the honda kits pretty aggressively in order to be competitive against other TWM retailers.

as I've said before, itb's should be the last part of the equation when building a motor. if you call TWM and tell them you plan on putting the aforementioned itb's on a stock motor, they'll tell you not to buy itb's. this (again as I've stated earlier) is why I don't care much for jimmy at fuji-racing. he has brain washed people into thinking that throttle response makes up for low horse power.

everyone here should know by now how the law of diminishing returns applies to building ANY motor. in order to get that last bit of horsepower you're going to have to spend a lot more money. given all this, itb's aren't for every, but if you have the budget and want the ultimate in all motor performance on the track, go for it.
User avatar
Savington
Stage 2
Posts: 688
Joined: Wed Jan 02, 2008 4:15 pm
Location: Mtn. View | San Luis Obispo, CA
Contact:

Re: IRTB goodies

Postby Savington » Wed Apr 09, 2008 4:35 pm

genghis ken wrote:i equate $2400 ITBs with 10-15hp increase to being the only one banging the office hottie. its a nice previlege that not everyone has.


I equate $2400 ITBs with 10-15hp increase to being the only one banging the office hottie, only to find out she has chlamydia and everyone else knew about it. You thought it was a good idea at the time, everyone else thought you were a retard and laughed at you privately, and now you feel (and look) like "that asshole".

Popstoy wrote:All that sex, and very little foreplay.


Fucking L-O-L.
Trackspeed Engineering
High-Performance and Road Race Miata Specialists
Racing engines, 949Racing 6UL wheels, suspension, brakes, and more!
Sunnyvale, CA | 650-701-RACE
User avatar
Ken P
Stage 4+
Posts: 10051
Joined: Tue Dec 04, 2007 12:14 pm
Car(s): 2014 NC GT
Car(s): 2013 Fiat 500 Abarth
Location: Jungles of Antartica

Re: IRTB goodies

Postby Ken P » Wed Apr 09, 2008 4:59 pm

just as long as i dont know about it, ill be ok. ignorance is bliss.
Member of the Brake Fade Society.

Keep up with RetroModern's latest products
Instagram: @retromodernusa
twmboy
Stage 1
Posts: 130
Joined: Thu Jan 24, 2008 5:04 pm

Re: IRTB goodies

Postby twmboy » Mon Apr 21, 2008 9:31 pm

some more pics I found on my comp from back in the days...

62mm rx7 kit; quad injectors

Image

427 kit built for Roush Racing

Image

Bmw 48mm s52 kit

Image

2900 series 45mm dcoe kit

Image

DVS honda thank you card

Image
User avatar
Ski_Lover
Stage 3
Posts: 1083
Joined: Fri Apr 11, 2008 9:44 pm
Car(s): 90 DP Miata, 1.8L
Car(s): 04 Prius
Car(s): 06 Tundra
Location: Campbell

Re: IRTB goodies

Postby Ski_Lover » Fri Apr 25, 2008 7:08 pm

twmboy wrote:seriously guys you'd be much better off with a compression bump before you went to itb's. in order to get 145 whp out of a miata with itb's you'd have to have a 99 head ($500), mildly aggressive cams ($750+), header ($450), exhaust ($300), engine management ($1500) and of course the itb's ( $2000). honestly putting on a set of itb's without the proper compression is a waste of time.


I'm sure the itb's look and sound awesome, and have great throttle response, but here's a pretty close comparison to the above. I just added a Megasquirt PNP & RX7 460cc injectors to my JRSC 1.6 Miata. It already had the JR Headers, High Flow Cat and Borla Exhaust, but I'm not counting those costs as I assume the above quoted 145 whp set-up has something similar for the exhaust.

Used JRSC M45, $1,500
Megasquirt PNP, $750
Used RX7 Injectors, $150
AFM Delete, $0 (used friend's old filter)
DynoTune, $185
Results: 143 WHP & 122 ft-lbs for ~ $2600

I also threw some bucks Andrew's way. He didn't ask for it, but his help was totally worth it to me. He helped with the install, Injector swap, and MSPNP set up. It saved me a lot of money I'd be sure to pay at the Dyno, and I'd rather be giving my hard earned bucks to him.

The car is amazing now. I get the awesome throttle response of a supercharger, and with the MSPNP I gained 19 HP, 22 ft-lbs mid-range torque, got rid of my idle droop problem, and the car pulls SO much smoother. The HP curve is more like a straight line. I can't wait to get my little monster out to AutoX and Track Days. The difference is huge.
Craig Northcutt

D-Prepared '90 Miata (TC Design Cage & Prep, Rebello built '00 1.8L NA, Ankeny Racing Custom Penske shocks, OSG superlock Diff, 949 15x10 6UL's, Hoosier Tires, 1924 lbs w/50# Rear Ballast)

Image

Return to “Power and Performance”

Who is online

Users browsing this forum: No registered users and 1 guest