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408 Fuel System
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Jun 02, 2014 11:11 am    Post subject: 408 Fuel System Reply with quote

Hi All,
Decided to make a new thread. The Pro-Jection system with 2 test sessions under my belt it is getting to a point where it might be done. As expected now that the pressure is high enough to deliver the required fuel at WOT the idle cannot be leaned out enough. Basically the duty cycle with this much fuel cannot be adjusted low enough with the controller. I still have to try some more but that is what I see. The EZ-EFI 2.0 might not be my choice but the XFI Sportsman with the EZ-EFI 2.0 throttle body is looking better and better. The Sportsman has the ability to be set to control this throttle body and the tune can be locked. This will be a viable solution if I can't get it right. I did think about varying the fuel pressure but that gets dicey.
Paul

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Mon Jun 02, 2014 11:42 am    Post subject: Reply with quote

I'm kind alike you - I can think of ways to possibly adjust fuel pressure but I can see why you wouldn't want to go that route. I'm going to work on some assumptions on this idea. I'm wondering if you could possibly retune the range of adjustment on the idle fuel pot by changing it to a different ohm range. I have no idea how this would affect the transition off idle though or what other quirks this might cause. Clay
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Jun 02, 2014 1:24 pm    Post subject: Reply with quote

Hi Clay,
One interesting thing about this system was that it ran the fuel pump at varied voltages originally through the fuel pump connector out of the ECU. What I did do per Holley's recommendation to keep steady fuel pressure because of demand was install a relay and switch it with the original ECU fuel pump circuit. Now that I am up at 28PSI maybe it would be worth a try? The problem is that it might not supply enough current to the pump which was the original issue with the system. I was going to explore this option too.
Paul

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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SMOKEmUP
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Joined: 30 May 2002
Posts: 3169

65097.54 points


1979 Chevrolet Camaro

PostPosted: Mon Jun 02, 2014 2:00 pm    Post subject: Reply with quote

How many injectors do you plan on running?
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Paul P
Member


Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Jun 02, 2014 2:04 pm    Post subject: Reply with quote

With the system I have in mind it has 8 but will run 4 at idle for control of the fuel delivery.
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Mon Jun 02, 2014 5:58 pm    Post subject: Reply with quote

I would think it would have to reduce voltage a lot for fuel pressure to drop at idle since it's such a low flow situation. I was thinking the systems that reduce voltage to the pump were more for pump longevity than anything else. How about this - put a bleed / bypass in the pressure line controled by a solenoid. Then you could control the solenoid with a throttle microswitch or rpm switch. Then by sizing the bleed / bypass orfice you could control idle pressure. Should be pretty reliable / repeatable. Don't know if it'd get you what you need - thinking out loud. If you use the original power supply you could put a relay on a w.o.t. microswitch to supply the pump at high demand situations. Clay
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Jun 02, 2014 6:15 pm    Post subject: Reply with quote

Either way I can throw a gauge on it to see what the difference in pressure is. I might be able to get away with this yet. I did find the XFI ECU and EZ-EFI throttle body for slightly under $2700. Surely would not want to spend it if I don't have to. This is so close I can taste it.
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Mon Jun 02, 2014 7:01 pm    Post subject: Reply with quote

Heck no I wouldn't give up yet. What you're doing is sorta like a blow thru carburetor - so many people just think it won't / can't work. If you can make it work it'll be neat that what I'm sure is looked at as an archaic system can be made to work pretty well. Clay
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Tue Jun 03, 2014 10:58 am    Post subject: Reply with quote

I did think of one thing that might solve this problem. The old drill a hole in the throttle plates trick that was used in many cases to keep the curb idle slots from being exposed on some 2bbl applications as well as some other carbs. For this system it would let more air in and lean out the idle without changing the TPS position. If that is all I need to do I could be ok. Still have to find time to get away from the honey do list to test it.
Paul

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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Big Dave
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Joined: 04 Dec 2005
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Location: Tampa Florida
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PostPosted: Thu Jun 05, 2014 12:44 pm    Post subject: Reply with quote

I know next to nothing about EFI compared to you guys but if the throttle plate is similar to the Holley there is another alternative to drilling holes in the throttle plates to increase air feed at low RPM.

As I understand it EFI doesn't have an idle circuit separate from the ruin circuit the way a carb does. So I agree with you that fiddling with the fuel pressure will introduce more problems than it solves.

If they have a secondary throttle stop the same way that a Holley four barrel does; you can adjust the angle of the secondaries at idle to increase air flow without affecting the throttle position sensor. It may be close enough to the Holley to use the Holley external adjustment kit that allows you to adjust the secondarties as the car is running instead of trial and error of removing the throttle body adjusting a trying it out then repeat until you find a happy medium.

Big Dave
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Thu Jun 05, 2014 3:07 pm    Post subject: Reply with quote

Hi Dave,
This unit is not progressive all 4 throttle plates move at the same time thus moving the TPS. The secondary idea although a good one is not viable with this setup.
Thanks,
Paul

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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View user's profile Send private message
Paul P
Member


Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Jun 16, 2014 1:18 pm    Post subject: Reply with quote

Got out and tested again. Not easy to find time and my sticker has a 5 on it DOOH! Idle and warmup/choke seem to be ok now. Part throttle is nice too and it is fat up top. One thing I did try on this test session was backing down the Accel circuit. Since there is a lot of fuel pressure it still never hesitated with it at the max low setting. It did seem to drive ok. I have to get some dyno time. Blasting up to 100+ MPH frequently on the street testing is fun but a big ticket would suck.
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
Back to top
View user's profile Send private message
SMOKEmUP
PostMaster


Joined: 30 May 2002
Posts: 3169

65097.54 points


1979 Chevrolet Camaro

PostPosted: Wed Jun 18, 2014 11:01 am    Post subject: Reply with quote

Dyno time would be much easier to get it dialed in.

On a side note I'd love to see the dyno operators face when you start tuning the pro-jection.

_________________
Stop running from your pain and embrace your pain. Your pain is going to be a part of your prize.

I challenge you to push yourself.
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View user's profile Send private message Visit poster's website
Paul P
Member


Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Wed Jun 18, 2014 4:03 pm    Post subject: Reply with quote

True. I am dyno ready. Just have to strap down the car and dial up the tune!
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
Back to top
View user's profile Send private message
Paul P
Member


Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Fri Jun 27, 2014 10:28 am    Post subject: Reply with quote

Looks like dyno tuning will be the next step after getting a sticker on the car this weekend. I'll be at ESP in Sterling Mass. on July 12 if I can get a confirmed appointment. Smoke might want to add this place to the dyno list.

http://www.enhancedstreetperformance.com/dyno-tuning-pricing

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
Back to top
View user's profile Send private message
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