[Formulajones]

Originally Posted by JLMounce

No, none of the TBI systems must control timing. They will if you want them to, but it's not needed. There are several FiTech models in fact that don't even offer the ability to do so.

The only one discussed here that absolutely does require timing control is the Edelbrock Pro Flow system. Because it's MPFI, it needs to know which cylinders are firing and when in order to provide accurate fueling.

Based on what hwystr is saying though, it sounds like the Sniper will control an MSD billed distributor as well.

Okay that's good enough for me. I don't absolutely need it to control the timing. It's already dialed in perfectly, but I have the option to try, if it doesn't like it I can revert back to no control over timing.

That scenario works for me.

[ta man]

Its interesting in all these posts..no one has reported mpg gains..which the novice or average tuner should see swapping from carb to FI.

[Formulajones]

I think someone like myself will see mpg gains simply because I'm constantly changing elevations.

I can pretty much dial in a carb to run stoich at idle, right off idle transition areas, and light throttle cruise without much fluctuation. So I likely wouldn't see a huge gain in mpg going EFI, but what will change for me is that the EFI will constantly adjust for that stoich number as my elevation goes up and down.

That will be the biggest benefit, plus the added crispness and response as it adjusts to a proper AFR for the changing elevation. I would imagine the plugs will stay a bit cleaner as well.

With that said, I'm not even looking to do this on our daily drivers, both of which are carbureted. I'm looking to do this on a couple of weekend fun toys that don't see but ~5,000 miles a year, so mpg isn't the first concern.

[Scott65]

Originally Posted by HWYSTR455

Yeah,maybe, but you still have to phase it.


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There's no maybe on the crank trigger being more accurate.

[JLMounce]

Originally Posted by ta man

Its interesting in all these posts..no one has reported mpg gains..which the novice or average tuner should see swapping from carb to FI.

I haven't posted anything on this simply because I don't have before numbers to make a comparison and even then it would be almost meaningless because I had to purposely run my carb fat to try and keep the little men with hammers away.

At the time I had a #62 combo on top of a +0.030 455 and a comp 280H. Because I couldn't really run the car very hard nore for very long before I fought vapor lock, I was inclined to spend the $7.10 per gallon for 100 octane fuel.

When I went to the FiTech and could actually drive the car whenever and however without fear of it stalling all over the place, it quickly become an issue paying for that gas, so I went to a KRE top-end.

I can say that I get what I consider decent mileage with the system. Typically I get between 14-16mpg and that's without an overdrive and with a 3.73 final and 26" tall tires.

With the carb and previous setup, I think I calculated I was getting 9-11 mpg, but again that's not a fair measure because the combination was nowhere near optimal.

[67gtospud]

Originally Posted by ta man

Its interesting in all these posts..no one has reported mpg gains..which the novice or average tuner should see swapping from carb to FI.

I don’t track my mileage very close but When I was running throttle body efi I averaged 20mpg one weekend vs the 15mpg with my previous 2-4 carb setup.

[455'73inElCamino]

Originally Posted by 67gtospud

I don’t track my mileage very close but When I was running throttle body efi I averaged 20mpg one weekend vs the 15mpg with my previous 2-4 carb setup.

I haven't reported mileage because my car has only gone through one tank so I want more data.

Original engine was 13-14 best case. But overall mileage improvements will never pay for the sniper/fitech because the improvements aren't big enough and at least my car doesn't get driven enough.

I likely will go holley dual sync because I think it is the easiest thing to install. I would love to run a crank trigger but if you buy the kits they are expensive. I have seen people in videos setup crank triggers with GM parts but it is an effort to do so.

Also, why couldn't one run a wasted spark like Ford did. Doesn't that make things easy? Or are/were there problems with such a system?

[HWYSTR455]

Originally Posted by Scott65

There's no maybe on the crank trigger being more accurate.

Most of the advantages crank triggers have really don't kick in until higher RPMs, usually 7000 and above. Below that, the advantages are nominal.

When tolerances stack up, from say the timing chain and gear mesh, as in a high mile engine, that too would be a situation where a crank trigger shines.

Newer engines have a cam sensor that's actually using a reference/trigger that's in the cam core, and the ECUs have a way to compensate between the differences of crank & cam signal variances, which is beneficial in a sequential system, but in most cases we, using traditional engines, will never be able to take advantage of.

I guess you could make something, maybe using the rear cam tunnel plug, where it could be more accurate, but the level of effort would be questionable if it would be worth it.

Main reason I don't use crank triggers is due to the offset of pulleys. I have seen some who embed the magnets in balancers, but again, the level of effort for nominal gains is questionable.



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[455'73inElCamino]

I have 3 tanks of gas used up in my driving with the sniper on it.

with my now 3.42 gears, I am getting 11 mpg which is worse than my quadrajet even when taking into account the gearing change from 3.73 to 3.42s.

Part of the issue is the holley is runing 13.5:1 at idle (quad was set at 14-14.5), cruise is at 14 (quad was at 14.5-15), WOT both at 12.5.

My driving has definitely been mostly stop and go but I don't think it is really different than what I was doing before.

FWIW.

[HWYSTR455]

Why not try different AFRs? Ones closer to what the carb was at?

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[Formulajones]

Looks like the quadrajet was set up on the lean side.

You can command any AFR you want with the FI kits. I usually shoot for an area the car runs best in for best drivability, and not really shoot for a specific number, because every engine responds differently to that.

[455'73inElCamino]

Originally Posted by HWYSTR455

Why not try different AFRs? Ones closer to what the carb was at?

.

I do plan on trying different AFRs.

I ran the quadrajet more lean because I had a an HEI distributor that allowed more vacuum advance which enabled me to run it leaner under light throttle positions, and because the engine "allowed" it.

However, with the current build I can not fit the other distributor so I have an aftermarket distributor that only allows 10 degrees of advance. So it doesn't tolerate a leaner mixture. But I have not attempted to lean it out as of this time.

Next year my plan is to use timing control. We will see what happens then!

While the engine in its current configuration runs really well, I like many of us just can't let things be.

[leeklm]

"I like many of us just can't let things be"

Amen

Sent from my SM-G965U using Tapatalk

[HWYSTR455]

Timing control has many benefits, no more weights & springs, and you can program things like idle smoothing, high speed retards, max advance at idle and cruise, offset by TPS value, tons of stuff. It's worth it.

What's your timing at idle?

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[455'73inElCamino]

Originally Posted by HWYSTR455

Timing control has many benefits, no more weights & springs, and you can program things like idle smoothing, high speed retards, max advance at idle and cruise, offset by TPS value, tons of stuff. It's worth it.

What's your timing at idle?

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I don't recall for sure but I think it is only 12 degrees, 22 with the vacuum advance as I am running ported vacuum. Unported seems fine too.

My vacuum at idle (it can idle pretty well even down to 600 rpms) ranges from 12.5 to 13.5" depending on how everything is setup. right now it is set at about 13.5".

Vacuum is 22.5" slowing down from speed with throttle closed. That gives you the full range of what vacuums the engine can see.

I agree, there is a lot I can do with timing control.

[Dragncar]

Its been said before that a Q Jet done correctly is the closest thing to a throttle body FI. And a lot simpler.
GM only went to the throttle body when the last Q Jets got expensive enough to justify FI.

[carbking]

Interesting thread.

I will admit to absolutely zero experience with aftermarket efi, and that is by choice.

I have lots of experience with direct comparisons of older O.E. efi versus carburetion (where smog emission is not an issue); and have yet to see an older efi system that could compare with carburetion in cost or performance.

The real value I see in efi would be if I lived somewhere like maybe Colorado, where I drove through significant altitude changes daily. I can still adjust for it fairly easily on my Carters by changing metering rods/springs; but still have to spend 5 minutes to stop the vehicle, open the hood, and swap the parts. Easier to let the efi handle the altitude changes. My only issue with buying efi for this reason would be reliability; have spent waaaaaaaay more money proportionately on replacement of damaged electronics in the last 10 years than I have on carburetors in the last 60 years.

As far as magazine articles/tech answers supporting their advertisers; has been going on since at least the 1950's when I started reading car magazines. I pay little to no attention to these, would rather spend 15 minutes on the telephone with knowledgeable individuals whom I trust.

But the whole efi versus carburetor thingy is pretty much moot at this point in time. In 10 years, everything will be electric anyway; like it or not.

Nice to see a thread where several diverse opinions exist and no name calling.

Jon.

[shaker455]

Originally Posted by Steve C.

Dyno Test: Quadra-Jet vs Holley Sniper

https://www.hotrod.com/articles/1968...holley-sniper/


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Nice results Steve.
We do like the Holley system and have good results on Lenny Caverly's dyno when the customer ask for FI over carb.

[JLMounce]

Against the aftermarket TBI systems available right now, there's really no reason to think that the system will produce more power or better fuel economy than a well sorted carb. They do the same thing, provide batch fuel to an airstream. One does it mathematically based on sensors, the other does it analog via the venturi signal, jets and rods etc.

As you mention if you're in an area like I'm at where weather and altitude changes happen frequently, it's nice not having to even think about that. The EFI does it's job. No seasonal changes, no changes at the strip for altitude etc.

The majority of people buying these don't have a well sorted carb though, which is where you see performance and economy improvements.

As far as reliability is concerned, I've logged a bit over 10,000 miles on my FiTech and probably another 2000 or so on my wife's FiTech equipped car. I was having trouble keeping carbs from boiling fuel in the bowls so I was in an unreliable state to begin with on my deal. Even in 100+ degree weather I haven't had any issues anywhere. In the 4.5 years I've had this installed it's never left me stranded. I did have the main harness connector go south on me which required the purchase of a new connector and about 45 minutes to repin the harness. That deal cost me about 45 bucks.

The newer FiTech models addressed that issue. The early units were drawing more amperage in real world use than what they were seeing in testing. Models since about 2016 have a beefier main harness and connector as a result.

Once you get into MPFI systems where you can control spark and fuel more granularly, including timed injection and cylinder by cylinder spark and fuel mapping, the game really starts to change.

But, at least in my case, reliability hasn't been a concern at all with the TBI setup.

[HWYSTR455]

Originally Posted by JLMounce

... I was having trouble keeping carbs from boiling fuel in the bowls so I was in an unreliable state to begin with on my deal. ....

Another positive with EFi, the psi in the lines prevents any type of vapor lock especially with today's fuels.

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