enlarged throttle bodies, for a 2.0L 4 cylinder |
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enlarged throttle bodies, for a 2.0L 4 cylinder |
DanT |
Sep 20 2006, 11:28 PM
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#1
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Going back to the Dark Side! Group: Members Posts: 4,300 Joined: 4-October 04 From: Auburn, CA Member No.: 2,880 Region Association: None |
anybody out there using them on a stock D-jet FI system?
I am just about to start my motor rebuild and will be keeping my stock FI. Wanted to know if anyone is using currently, or has used, enlarged throttle body on their stock injection. If so, how did it work? notice any power increase? If any where in the rpm range? tuning issues? other motor mods along with the throttle body change. (IMG:style_emoticons/default/smile.gif) |
Trekkor |
Sep 21 2006, 12:20 AM
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#2
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I do things... Group: Members Posts: 7,809 Joined: 2-December 03 From: Napa, Ca Member No.: 1,413 Region Association: Northern California |
Andy Brian from RR-PCA uses a larger TB from a Volvo I believe.
KT |
Joe Ricard |
Sep 21 2006, 05:07 AM
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#3
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
What 44 IDF's are not big enough?
Oh, D-jet. Didn't Jake say that there isn't much to be gained? Stock stuff flows enough for much more HP. Something like that. Well except getting drop kicked to a higher racing class. |
Mark Henry |
Sep 21 2006, 07:51 AM
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#4
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
Yep, no gain...save your money
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Bleyseng |
Sep 21 2006, 08:20 AM
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#5
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
I bored my out to 50mm and had shaft bushing installed.
I think I get more outta the shaft bushings than the boring. (IMG:style_emoticons/default/dry.gif) Brad said once he tried both out on a dyno and the difference was 1 hp. |
Jake Raby |
Sep 21 2006, 08:26 AM
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#6
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Most of the time POWER WILL BE LOST!
Bigger isn't better- never, ever make that mistake! all the larger T/B will do on a stock engine is make the car drive worse! |
pbanders |
Sep 21 2006, 10:44 AM
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#7
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Senior Member Group: Members Posts: 939 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
Even if boring the TB improved the volumetric efficiency (VE) curve, with stock D-Jet, unless the engine speed mixture correction circuits in the ECU are modified for the new VE curve, you won't get any improvement in power or torque.
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gregrobbins |
Sep 21 2006, 11:07 AM
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#8
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Member: Team NARP Group: Members Posts: 1,515 Joined: 23-March 04 From: Arizona Member No.: 1,844 Region Association: Southwest Region |
Even if boring the TB improved the volumetric efficiency (VE) curve, with stock D-Jet, unless the engine speed mixture correction circuits in the ECU are modified for the new VE curve, you won't get any improvement in power or torque. Brad, good to see your recent post on the D-jet throttle body. I have appreciated your work and web page. Thanks for the effort. I still hope to meet you in person some time. Do I recall from the bird board you are having your motor rebuilt. Is that being done here in the valley? If yes, whom did you select to do the work. Jack? Tried to PM you, but got a message the box was closed/full Greg Robbins Glendale 602-291-3525 |
pbanders |
Sep 22 2006, 11:37 AM
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#9
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Senior Member Group: Members Posts: 939 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
Greg, yeah, Jack's doing the rebuild. Let's just say its proceeding at a "leisurely" pace (i.e. the car went in the shop in mid-April), but the work so far has been excellent. It's supposed to go back into the car this weekend, but I'm expecting it to take a few more weeks before I get the car back.
As soon as I have the car back together, I'll take it out to one of the local 914 runs. I did one a few years ago up to Sendona that was a lot of fun. Hope to see you there. |
Brad Roberts |
Sep 22 2006, 11:52 AM
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#10
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914 Freak! Group: Members Posts: 19,148 Joined: 23-December 02 Member No.: 8 Region Association: None |
Thanks for posting Brad (IMG:style_emoticons/default/clap56.gif)
Havent seen you here in awhile. No gain with larger TB/waste of time/money B |
DanT |
Sep 22 2006, 05:39 PM
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#11
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Going back to the Dark Side! Group: Members Posts: 4,300 Joined: 4-October 04 From: Auburn, CA Member No.: 2,880 Region Association: None |
Thanks for posting Brad (IMG:style_emoticons/default/clap56.gif) Havent seen you here in awhile. No gain with larger TB/waste of time/money B That is a surprise to me since several of the old time BP racers said it seemed to make quite a bit of differnce on their 2.0L cars. (IMG:style_emoticons/default/blink.gif) (IMG:style_emoticons/default/sad.gif) |
bd1308 |
Sep 22 2006, 06:42 PM
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#12
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
The deal with bigger TBs and not having the VE or the engine designed to take advantage of this, you'll find that the engine will have a higher value of high-rpm zip but lack very big in the low-end torque value.
MPGs will suffer as well too. Ive personally done some experiments on this very thing. It 'feels' faster, simply because the low-end grunt sucks so much, that people get all excited when it finally starts going... b |
Dave_Darling |
Sep 22 2006, 11:41 PM
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#13
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914 Idiot Group: Members Posts: 14,990 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
Charlie Davis bored his stock TB and made a new throttle plate. He claimed some "seat of the pants" improvement, once some tuning had been done to the D-jet. He even went so far as to fab up a throttle body of his own at one point! Sounds like the improvement from that last one was marginal or nonexistent.
No dyno runs that I know of. --DD |
bd1308 |
Sep 22 2006, 11:42 PM
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#14
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
I wouldnt be surprised to see less low-end power than stock and a bit more high-speed power than stock.
The seat of the pants factor is from the 'difference' between these two spectrums. |
Rand |
Sep 22 2006, 11:50 PM
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#15
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Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
Made me think of THIS THREAD. Interesting reading at least.
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bd1308 |
Sep 22 2006, 11:58 PM
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#16
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
exactly, its like taking 40IDFs and putting 48 velocity stacks on them or something.
It just doesnt work, most people prefer 32s or 38s i believe and it shows, our engines like more air velocity and the only way to do that is choke down the TB. |
DanT |
Sep 23 2006, 12:08 AM
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#17
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Going back to the Dark Side! Group: Members Posts: 4,300 Joined: 4-October 04 From: Auburn, CA Member No.: 2,880 Region Association: None |
so the moral of this story is that a 2.0L needs a smaller TB and/or plenum?
Hmmmm (IMG:style_emoticons/default/idea.gif) How about some sort of pyramid in the plenum under the TB? IF a stock TB and plenum was too large for a 2056 then it must be way too big for a stockish 2.0L. (IMG:style_emoticons/default/dry.gif) |
tradisrad |
Sep 23 2006, 10:11 AM
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#18
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Senior Member Group: Members Posts: 985 Joined: 11-September 06 From: San Mateo, CA Member No.: 6,815 Region Association: Northern California |
I thought of buying a T/B from high performance house that has been enlarged but I figured it was a waste of $250 as the performance would not be improved that much.
My T/B did not have the vacuume advance port on it, last night I added the vaccume advance port to my T/B. I do not feel any improvement in power however the car has smoother acceleration. So maybe if your T/B does not have the vacuume advance that may be worth adding. We bought a .157" brass tube from the local hobby shop and drilled a .154" hole in the port area, we went .4" deep and then finished off the hole with a .040" hole that went all the way into the T/B. We measuerd the stock hole (from a friends '73 2.0) and it was .040". At one point some one said that we should drill a .030" hole but that was smaller than the stock hole. |
pbanders |
Sep 23 2006, 04:40 PM
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#19
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Senior Member Group: Members Posts: 939 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
That is a surprise to me since several of the old time BP racers said it seemed to make quite a bit of differnce on their 2.0L cars. (IMG:style_emoticons/default/blink.gif) (IMG:style_emoticons/default/sad.gif) Yeah, but racers aren't streeters. A race car is operated closer to WOT and in high engine speed ranges continuously. With a larger TB and a richer mixture you can probably extract a few more HP, at a loss of low-end torque and some drivability - but on a race car, who cares? |
Jake Raby |
Sep 23 2006, 04:57 PM
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#20
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
The key is increased runner and plenum development. The throttle body seems to have the least impact on the engines I have tested.
Recently we outperformed a stock (large volume) 2.0L 914 plenum by using a stock 2.0 bus plenum with the stock throttle body being used on both. That arrangement tested back to back provided 153HP from a 2270cc engine, 13HP more than the larger volume 2.0 plenum. When my new dyno gets here I will be doing more of this development as I plan a new single T/B development for my DTM outfitted engines. |
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