Why EFI?, maybe excellence was expected and they came as close as they could.. |
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Why EFI?, maybe excellence was expected and they came as close as they could.. |
Gunn1 |
Jun 11 2016, 03:59 PM
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#1
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
Did Porsche eff up?
No they didn't eff up, they did the best they could with the new technology they had. It seems as though the technology was purchased by the folks at Bosch from the aviation component of Bendix. That said most Injection systems were originally good at idle and full open throttle, so primarily racing applications. So in there infancy not well suited for automobile applications. Been reading on different types of fuel delivery systems and their pro and cons. There are very few con's to todays EFI systems, there were however performance and reliability issues with the original designs. Even today Claims of increased HP, Fuel economy, drivability, reliability and so on....some still dispute how much these differences really mean. It appears the main thing EFI does extremely well over Carbs is in the pollution factor, or in this case the ability to pollute less. Carbs are a some what open system allowing hydro carbons to escape/vent in to our atmosphere even when the engine is at rest, where as the EFI is essentially a closed system releasing no vapors or gases unless the engine is running and those gases are then coming out of the tailpipe from the exhaust cycle. Many of the Guru's (about 5 to 1) prefer carburation. The above Statement isn't correct, although what confuses this OP is the sheer amount of photographic evidence on this site and others including evilbay and CL showing most engine compartments with Carbs installed. Many here have spent thousands on their cars, and what do you see when the lid is lifted? a Carburated engine..... So while my intentions will be keeping my cars in their stock or near stock form, with EFI, I cannot understand why so many Carburated cars. (Because its easy isn't an answer, because its simple isn't an answer and because its cheap isn't an answer) With this being the case, Did Porsche mess up when they went the EFI route with the 914? I do not believe they messed up, I believe they did the best they could with the available technology they had. Granted they did sort of use the end user as of a kind of a guinea pig/test bed, but what manufacturer doesn't in some way. WHY DID THEY DO IT????? I think that just as much as seeing the Ljet and Djet as a performance and platform to develop future EFI systems off of, Porsche and others also incorporated EFI into there products to show they were progressive company's in design and practicality. EFI, Unibody, Targa, Mid engine, four wheel disc, and many more attributes can be cited as Porsches View into the future. I would like to keep my car stock with the factory EFI, but increasingly getting more difficult to do with so little information backing it up. Above statement is also incorrect. In my case I think I am fortunate because I believe I have most the parts needed to reinstall the factory EFI's on all three of my cars. There is a plethora of info on both sides, but for now.... just for originalities sake, EFI will be the way I go. To those that added constructive comments and or facts to this thread... it is much appreciated...to those that took this thread as some sort of attack on their beliefs, or way to "clutter" the site, I can appreciate how you feel, but I just see those arguments as shutting down the free flow of ideas and the give and take of facts that get each of us to arrive at our own understanding of the information. |
gereed75 |
Jun 13 2016, 11:44 AM
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#2
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Senior Member Group: Members Posts: 1,244 Joined: 19-March 13 From: Pittsburgh PA Member No.: 15,674 Region Association: North East States |
Thanks Brant, First let me say that I also consider it a non-problem. Partly just illustrating the point about how deficient even well tuned carbs can be...but I would also like to get it better.
The engine is a 2.4 with some head work done, DC 30 cams and 9.5 CR, single plug. I have played a bit with emulsion tubes and am running F26's with 32mm venturi's. Idle AFR's are around 12 (hard to tell, they vary alot). From everything I have read and all I have talked to, the idle airs seem to be a definite factor. But, as you know they are pressed into the IDA 3C body. Please tell me more about float levels. Mine are set "stock". I guess lowering them might effect the idle circuit towards lean??? Thanks man, now this thread is getting constuctive! PS.... love your car |
brant |
Jun 13 2016, 03:19 PM
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#3
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914 Wizard Group: Members Posts: 11,622 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
Thanks Brant, First let me say that I also consider it a non-problem. Partly just illustrating the point about how deficient even well tuned carbs can be...but I would also like to get it better. The engine is a 2.4 with some head work done, DC 30 cams and 9.5 CR, single plug. I have played a bit with emulsion tubes and am running F26's with 32mm venturi's. Idle AFR's are around 12 (hard to tell, they vary alot). From everything I have read and all I have talked to, the idle airs seem to be a definite factor. But, as you know they are pressed into the IDA 3C body. Please tell me more about float levels. Mine are set "stock". I guess lowering them might effect the idle circuit towards lean??? Thanks man, now this thread is getting constuctive! PS.... love your car thanks for the compliment the float level will change which emulsion tube holes are exposed and have a big impact on part throttle mixture. might be worth playing with (its free) and checking its effect with an AFR but like you said.... not a big deal really... not an issue that sounds like a fun motor! we play with air corrections depending on certain corners at certain tracks.. that cause certain RPM/gearing outcomes so If I have a flat spot as I transition to mains in a certain corner (lower rpm), that is causing me problems on the track, I can often move that transition point with air corrections to benefit one certain corner.... plus humidity and temp change through out the day I often run different jets in the afternoon or different jets on sunday... than I did on Saturday morning. This is due to running too large of primary venturi's and essentially over carbureting a 2.0 motor. (loss of air speed/velocity for correct atomization at 4,000 -5,000 rpm) but I only care about redline output so this is the way it is for a race car right now I'm running 35mm venturi's on a 2 liter at 6,000 foot of elevation. mains are usually around 175 or 180mains depending on the weather of the day I carry everything up to around 215 mains for lower altitude tracks I'm also running IDS carbs on this motor, and the 2ndary enrichment tubes really benefit mixture above 7,000rpm. You can literally see them kick in on the AFR gauge. They have to prime themselves, and are very noticeable on the mixture when they aren't working the first 3 times you run up to redline. The factory installed them for a reason on the S cars.... even though it was a one year change, right before they went to MFI (they even made the 2ndary enrichments in 3 different jetting sizes... but impossible to find) brant |
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