 Has anyone ever used D-jetronic on Individual Throttle Bodies? |
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| gothspeed |
 Aug 23 2009, 12:58 PM
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#1
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Senior Member  Group: Members Posts: 1,539 Joined: 3-February 09 From: SoCal Member No.: 10,019 Region Association: None  |
Since it is manifold pressure based and manually adjustable, with some tweaks it should work ..... right??
My 914 is a 1973 1.7 ...... so I was thinking of going with 1911cc kit and tweaking the D-jet. So just a question to see if anyone had tried D-jet Individual Throttle Bodies or if anyone thinks it would work? (IMG:style_emoticons/default/smile.gif) Is 100 HP possible from a 1911cc with ported exhaust ports, stock D-jet and stock cam? |
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| CliffBraun |
Aug 23 2009, 02:41 PM
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#2
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Member Group: Members Posts: 252 Joined: 26-April 06 From: San Luis Obispo,ca Member No.: 5,933 Region Association: None |
The way I see it it could probably be made to work with some adjustment. What the CB performance efi does for MAP is take vacuum from a tap on each throttle body and merge them to a map sensor (think they also do idle air motor on this line).
My question is why bother? do you have all the parts laying around? On a mild engine you're really probably not gonna gain too much through the less restrictive intake tract and you're adding a lot of complexity. I'd say 100HP is possible from 1911 with ported heads and a stock cam, not sure about the EFI. I have stock two liter stroke and bore and nice heads and several other modifications and our official guess for power is 130-140HP. |
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| Bleyseng |
Aug 23 2009, 03:07 PM
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#3
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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 |
QUOTE(gothspeed @ Aug 23 2009, 11:58 AM)  Is 100 HP possible from a 1911cc with ported exhaust ports, stock D-jet and stock cam? no, the stock cam limits it too much |
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| jcd914 |
Aug 23 2009, 03:10 PM
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#4
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Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
I have though about this from time to time because I do have a set of manifolds and individual throttle bodies sitting out in the garage (or somewhere). The complications I foresee are the Manifold pressure hook up, Intake Air Temperature sensor location and the cold start valve location. I wonder if tapping all 4 intakes for manifold pressure would give a smooth enough vacuum signal for the MAP sensor or would it exaggerate the pulses to the point the MAP was confused.
Quite possibly the performance increase would be insignificant if the heads and exhaust can flow any more air that the stock intake can provide. But since carbs seem to wake up a stock engine I would think if the FI could provide fuel to go with the air from the individual throttle bodies then it should work as well as carbs. Jim |
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| Bleyseng |
Aug 23 2009, 03:14 PM
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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 |
adding Carbs to a stock engine IMHO doesn't wake up the engine...using the stock cam is the limiting factor not the FI. Carbs seem to wake it up with all that noise they make.
Now adding a carb cam and dual carbs wakes upa 2.0L fo sure... |
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| Dave_Darling |
Aug 23 2009, 05:04 PM
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#6
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914 Idiot Group: Members Posts: 14,984 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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You can probably convince it to run, but it'll never run right. The massive vacuum fluctuations as the valves open and close will confuse the heck out of the system. You can even those out if you tap into all four manifolds and combine the signals, preferably with enough volume to damp the pressure waves. Which gets you back to having a common-plenum system, if the "taps" and the "combiner" are large enough.
I recall that some MS people have gone with a "combined" setup that uses throttle position from idle to half-throttle or so, and MAP above that. It sounded like it worked OK, a little bit better than a pure alpha-N system, but wasn't worth the bother. And that's on a completely-programmable system. --DD |
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| Chris Hamilton |
Aug 23 2009, 05:42 PM
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#7
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Senior Member Group: Members Posts: 611 Joined: 7-March 06 From: Berkeley, CA Member No.: 5,687 |
QUOTE(Bleyseng @ Aug 23 2009, 02:14 PM) adding Carbs to a stock engine IMHO doesn't wake up the engine...using the stock cam is the limiting factor not the FI. Carbs seem to wake it up with all that noise they make. Now adding a carb cam and dual carbs wakes upa 2.0L fo sure... I'll have to disagree with that. I have a stock cam in my 2.0 with ported heads, long conrods and dual 40mms, and while it runs out of steam at around 6k rpms, it is much stronger than an injected engine. |
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| gothspeed |
Aug 23 2009, 05:43 PM
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#8
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Senior Member Group: Members Posts: 1,539 Joined: 3-February 09 From: SoCal Member No.: 10,019 Region Association: None |
I was hoping to not need a cam because I did not want to split the case (IMG:style_emoticons/default/sad.gif)
As far ar the vacuum fluctuations .... after hooking them all together they can be dampened using a 'restrictor' ...... a sensitive vaccum gauge on it during restrictor sizing, can give a good visual on those disturbances. ..... the reason I was thinking about Individual Throttle Bodies was to hopefully gain a tad on the 1.9 ...... because the stock manifolds are sized for a 1.7 ...... not to mention ..... ITBs would look very cool ..... (IMG:style_emoticons/default/biggrin.gif) |
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| Chris Hamilton |
Aug 23 2009, 05:45 PM
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#9
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Senior Member Group: Members Posts: 611 Joined: 7-March 06 From: Berkeley, CA Member No.: 5,687 |
Talk to Claudes Buggies performance about EFI. They have everything you need.
http://cbperformance.com/ |
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| gothspeed |
Aug 23 2009, 05:54 PM
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#10
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Senior Member Group: Members Posts: 1,539 Joined: 3-February 09 From: SoCal Member No.: 10,019 Region Association: None |
QUOTE(Chris Hamilton @ Aug 23 2009, 04:45 PM) Talk to Claudes Buggies performance about EFI. They have everything you need. http://cbperformance.com/ Like these??? (IMG:style_emoticons/default/biggrin.gif) http://cbperformance.com/catalog.asp?ProductID=412 The cool thing about this ..... if it works ..... I can drive around till I save up for 'programmable' FI to add to these ITBs should I decide to build up the engine futher (IMG:style_emoticons/default/smile.gif). |
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| Chris Hamilton |
Aug 23 2009, 09:00 PM
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#11
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Senior Member Group: Members Posts: 611 Joined: 7-March 06 From: Berkeley, CA Member No.: 5,687 |
I'm not sure the stock EFI system is going to be flexible enough to run something like that. It has a hard enough time working at all with a stock configuration, this is going to be a whole new ballgame in MAP sensor readings and fuel maps.
Those 48mm TBs might also be a bit large, but I'd talk to CB about that. Give them a call next week, they're very helpful. Best bet is probably going to be their Quick Tune EFI that programs itself as you drive. |
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| sww914 |
Aug 23 2009, 09:36 PM
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#12
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Advanced Member Group: Members Posts: 2,439 Joined: 4-June 06 Member No.: 6,146 Region Association: None |
QUOTE(Chris Hamilton @ Aug 23 2009, 04:42 PM) QUOTE(Bleyseng @ Aug 23 2009, 02:14 PM) adding Carbs to a stock engine IMHO doesn't wake up the engine...using the stock cam is the limiting factor not the FI. Carbs seem to wake it up with all that noise they make. Now adding a carb cam and dual carbs wakes upa 2.0L fo sure... I'll have to disagree with that. I have a stock cam in my 2.0 with ported heads, long conrods and dual 40mms, and while it runs out of steam at around 6k rpms, it is much stronger than an injected engine. He said stock engine, that's not stock. |
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| CliffBraun |
Aug 23 2009, 09:54 PM
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#13
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Member Group: Members Posts: 252 Joined: 26-April 06 From: San Luis Obispo,ca Member No.: 5,933 Region Association: None |
QUOTE(sww914 @ Aug 23 2009, 08:36 PM) QUOTE(Chris Hamilton @ Aug 23 2009, 04:42 PM) QUOTE(Bleyseng @ Aug 23 2009, 02:14 PM) adding Carbs to a stock engine IMHO doesn't wake up the engine...using the stock cam is the limiting factor not the FI. Carbs seem to wake it up with all that noise they make. Now adding a carb cam and dual carbs wakes upa 2.0L fo sure... I'll have to disagree with that. I have a stock cam in my 2.0 with ported heads, long conrods and dual 40mms, and while it runs out of steam at around 6k rpms, it is much stronger than an injected engine. He said stock engine, that's not stock. Hmm, well it's a stock cam still, but he's got FAR better heads, this gentleman has a comparable engine except for the con rods. I'd say chris' engine is better (rabbit rods is a great combo) but I can still see 100HP outta a stock setup with proper induction. I've felt the power difference between stock FI and carbs. One has to remember the entire reason for FI was emissions, and it was before they figured out how to achieve good power and emissions. |
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| fiid |
Aug 23 2009, 10:03 PM
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#14
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Turbo Megasquirted Subaru Member Group: Members Posts: 2,827 Joined: 7-April 03 From: San Francisco, CA Member No.: 530 Region Association: Northern California |
I think you'll find the manifold signature is way to lumpy for a D-Jet to work. All the manifold pressures will be higher because you'll have a throttle plate that is effectively 4 times larger; plus you won't have a plenum chamber or any of the piping.
You *might* be able to get it to run (and by run I mean idle). There are various tricks you can employ to make the D-jet run leaner or richer, like the knob on the top of the brain, messing with the CHT resistance, or changing the fuel pressure. The issue I think you'll run into is that getting it to basically run is totally different from having it run anywhere near correctly. You've got to worry about intake temperature, idling being different from higher rpm running, acceleration enrichment, plus having the basic shape of the map correct. I have some experience trying to get megasquirts to run with unstable map readings (on a cammed 2056), and it's a bit of a nightmare. We didn't have a lot of success with Alpha-N either. Not to say it can't be done, but I wouldn't put it in the easy category. |
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| gothspeed |
Aug 24 2009, 11:01 AM
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#15
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Senior Member Group: Members Posts: 1,539 Joined: 3-February 09 From: SoCal Member No.: 10,019 Region Association: None |
Thanks for the spirited responses ....... I will probably try smaller TBs first ....... (IMG:style_emoticons/default/smile.gif)
I really enjoy this kind of stuff ....... projects that are difficult, a pain in the rear or even seemingly impossible are only invitations ........ (IMG:style_emoticons/default/stirthepot.gif) If anyone has any more experience, knowledge, encouragement or discouragement they would like to share ...... please post up ...... (IMG:style_emoticons/default/biggrin.gif)!!! |
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| SirAndy |
Aug 24 2009, 11:13 AM
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#16
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Resident German Group: Admin Posts: 41,634 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Chris Hamilton @ Aug 23 2009, 03:42 PM) I'll have to disagree with that. I have a stock cam in my 2.0 with ported heads, long conrods and dual 40mms, and while it runs out of steam at around 6k rpms, it is much stronger than an injected engine. Did you compare your setup to a FI engine with the same mods? Because otherwise it's apples and oranges ... (IMG:style_emoticons/default/shades.gif) Andy |
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| brant |
Aug 24 2009, 11:41 AM
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#17
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914 Wizard Group: Members Posts: 11,623 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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its been done
two vintage racers in my club run individual throttle bodies on their 1.7's with Djet. They use 4 throttle bodies from the 2.0 it can work at wide open throttle not good at idle or street driving you won't like it for daily use alot of work for minimal gain possible though b |
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| fiid |
Aug 24 2009, 05:18 PM
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#18
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Turbo Megasquirted Subaru Member Group: Members Posts: 2,827 Joined: 7-April 03 From: San Francisco, CA Member No.: 530 Region Association: Northern California |
QUOTE(gothspeed @ Aug 24 2009, 10:01 AM) If anyone has any more experience, knowledge, encouragement or discouragement they would like to share ...... please post up ...... (IMG:style_emoticons/default/biggrin.gif)!!! Yeah. Sorry. Didn't want to be all discouraging and shit. That's not cool (on my part). You could TOTALLY get this setup working with Megasquirt. Megasquirt is a fun and not horrendous project to get running; and it can be done on the cheap. If you were diligent you could convert an engine to run on it in a day. You can use nearly all of the D-jet parts too (same injectors, fuel pump, relay board, the MAT sensor can work too. Throttle body could work if you weren't going ITB. |
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| r_towle |
Aug 24 2009, 05:29 PM
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#19
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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If you run a vacuum line to all four throttle bodies, then merge that into a small vacuum chamber...like a spherical vacuum system, it may work.
You would need to vent the vacuum chamber somehow? not sure Rich |
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| gothspeed |
Aug 24 2009, 09:11 PM
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#20
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Senior Member Group: Members Posts: 1,539 Joined: 3-February 09 From: SoCal Member No.: 10,019 Region Association: None |
QUOTE(brant @ Aug 24 2009, 10:41 AM) its been done two vintage racers in my club run individual throttle bodies on their 1.7's with Djet. They use 4 throttle bodies from the 2.0 it can work at wide open throttle not good at idle or street driving you won't like it for daily use alot of work for minimal gain possible though b QUOTE(fiid @ Aug 24 2009, 04:18 PM) QUOTE(gothspeed @ Aug 24 2009, 10:01 AM) If anyone has any more experience, knowledge, encouragement or discouragement they would like to share ...... please post up ...... (IMG:style_emoticons/default/biggrin.gif)!!! Yeah. Sorry. Didn't want to be all discouraging and shit. That's not cool (on my part). You could TOTALLY get this setup working with Megasquirt. Megasquirt is a fun and not horrendous project to get running; and it can be done on the cheap. If you were diligent you could convert an engine to run on it in a day. You can use nearly all of the D-jet parts too (same injectors, fuel pump, relay board, the MAT sensor can work too. Throttle body could work if you weren't going ITB. ..... as for 'nay sayers' ...... they are everywhere ...... and they usually talk like they have stake in the matter/project ............ (IMG:style_emoticons/default/wink.gif) I will try the D-Jet first ...... then try some other aftermarket programmable FI ...... like megasquirt as you suggested ......... thanks for the posts ... (IMG:style_emoticons/default/biggrin.gif)!!! QUOTE(r_towle @ Aug 24 2009, 04:29 PM) If you run a vacuum line to all four throttle bodies, then merge that into a small vacuum chamber...like a spherical vacuum system, it may work. You would need to vent the vacuum chamber somehow? not sure Rich |
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