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EFI with sidedrafttbi.com?

R

rootesrefuge

Donation Time
OK, I'm looking for input...

I built a 1725 for my daily driver '67 Arrow wagon. Tried using Alpine GT carbs, but just can't get the smog-era carbs to work to my satisfaction. Add to that the typical problems of running Strombergs on modern fuel, and converting to EFI keeps looking better and better.

There's a guy who's developed a kit to convert CD150 and CD175 Strombergs into TBI throttle bodies, check out sidedrafttbi.com. Seems like a really simple conversion. But their electronics package can't handle a twin carb 4 with 1-3-4-2 firing order, they only do kits for single carb fours. I have a single carb intake I could use, but would rather keep the duals.

Well, MegaSquirt to the rescue. Complete tunability, and capable of simultaneously firing both injectors. Reasonable price and good technical support, plus it doesn't require changing the ignition system. Sounds perfect.

Any opinions? Anybody running MegaSquirt on anything, Sunbeam or not?

Jon Arzt
Omaha, NE USA
 
B

Bill Blue

Platinum Level Sponsor
Opinions? Yeah, I have a couple. I looked into this sort of thing a while back, using the Zenith dual manifold. I could not find a TBI that I thought was small enough, as you must use two of them. I'm sure it would run like a scalded dog on top, but load up at low speed.

How about modifying the intake manifold to accept individual injectors? Or mounting a large injector up through the bottom of each Strom and run it with MegaSquirt?

Bill
 
R

rootesrefuge

Donation Time
That's the beauty of the sidedrafttbi setup. Take the pistons out of the carbs and replace them with machined inserts, each holding a GM TBI injector. Instant throttle bodies - the stock throttle butterflies control incoming air, even the stock choke pull operates the fast idle. Use the existing linkages, air cleaners, everything.
 
64beam

64beam

Donation Time
Hi Jon,

Were you looking at only modifying your existing setup or purchasing a complete new intake with throttle bodies? If I have the money to set it up, I would buy throttle bodies to replace my side draught setup on my car and couple it with a programmable efi computer. Thinking about it, if I went to that trouble I would do a twin cam transplant :confused: . There are people on this forum who dable in efi, so hopefully they can better advise you than me.

Regards, Robin.
 
R

rootesrefuge

Donation Time
For me, this isn't about maximum performance - it's about driveability and economy. My goal is to improve the behaviour of the engine since it has to run on today's fuel, and making the car more economical is a big plus. By using the stock carbs as throttle bodies, it keeps the costs way down and makes the installation dead easy. The whole conversion should be able to be done for under $600 with careful shopping.
 
64beam

64beam

Donation Time
rootesrefuge said:
For me, this isn't about maximum performance - it's about driveability and economy. My goal is to improve the behaviour of the engine since it has to run on today's fuel, and making the car more economical is a big plus. By using the stock carbs as throttle bodies, it keeps the costs way down and makes the installation dead easy. The whole conversion should be able to be done for under $600 with careful shopping.
Click to expand...

Hi Rootesrefuge,

How many extra miles do you gain by changing to EFI? The reason I ask this question is that alot of Alpine's both stock and worked return very good fuel ecomony and driveablility without EFI comparable with today's modern engined fuel injected cars.

Regards, Robin.
 
R

RootesRacer

Donation Time
Megasquirt only controls 2 injector phases, so for a 2 point TBI setup, megasquirt would probably not be too bad, if you were trying to do a 4 injector setup, I would probably try to talk you out of megasquirt.
 
R

rootesrefuge

Donation Time
Well, to quote the website:

"in around town driving of about a 100 miles, the car went from 18MPG with carbs, to 27 MPG. The car is wonderfully smooth and a pleasure to drive."

Of course, that's describing a TR6, so I would expect different numbers but very possibly a similar percentage. With anywhere near a 50% increase in mpg, it wouldn't take long to pay for the conversion. Add the fact that at the 15psi or so that the tbi system runs at, the boiling point of the fuel will be much higher. The fuel bowls that hang so close to the exhaust manifold will now be totally empty, making vapour lock a thing of the past.

For the reasonable costs involved, I figure it's worth a try. Keeping the original manifolds, carbs, linkages, choke, and air cleaner in place make it a very sweet, simple conversion. I've figured out the bits required, and will start ordering them up shortly.

I'll keep in touch with my progress!

Jon Arzt
Omaha, NE USA
 
alpine_64

alpine_64

Donation Time
I'm not saying that carbs are better than EFI, however, take the TR6 comparison with a grain of salt. How well were his carbs setup? What condition were his carbs in? Its possible the carbs were not runnign at their optimum. People often change things and say how much better it is, when they had not addressed the original issue
 
64beam

64beam

Donation Time
Hi Rootesrefuge,

I am by no means a guru in EFI, but gaining that such a big jump in MPG would suggest your carbies were not in good condition as Michael also pointed out. Would 10-20% be more realistic if any at all?

Regards, Robin.
 
B

Bill Blue

Platinum Level Sponsor
Jon, before ordering, consider this.

The "squirters" they are using on the TR6 are will fuel a 3.4 liter engine, there are two of them, so you have enough capacity to fuel a 6.8 liter engine. They are fueling a 2.5 engine, so they have 2.7 times the fuel delivery potential needed. You will be fueling a 1725 engine, so will have nearly 4 times the capacity needed.

This is a situation where bigger is not better. Fuel volume delivered by the injectors is not a smooth slope down to zero. Every time the TBI's fire, they deliver a minimum amount of fuel. I think this minimum is probably marginally okay for the 2.5, but greater than needed at low engine speed for a smaller engine. This causes the fuel loading problems for the MG's, not the different firing order.

If instead, two injectors for the GM multiport injected 2.8 four were used, I believe this problem would go away as they would be functioning within their design range.

But I am not an expert in this field, Jarrid is. This is a distillation of an exchange between he and I about a year ago when I was looking at the Zeniths. Better check with him before laying out the bucks.

Bill
 
V

V6 JOSE

Donation Time
64beam said:
Hi Rootesrefuge,

I am by no means a guru in EFI, but gaining that such a big jump in MPG would suggest your carbies were not in good condition as Michael also pointed out. Would 10-20% be more realistic if any at all?

Regards, Robin.
Click to expand...
There is no way that your old carburetors could ever be as efficient as fuel injection. Fuel injection can be set up to read the requirements of the engine many times a second and keep the mixture at the optimum ratio all the time, where a carburetor can't hope to duplicate that kind of precision. The carburetor works, but not as precise as fuel injection can. Someone once said that a carburetor is a controlled leak device, and that is true.

I wouldn't be surprised if the results would be as dramatic as that quoted. Manufacturers were forced to go to fuel injection in order to help control emissions, but primarily to increase gas mileage. If you could put a correctly calibrated carburetor set up and compare it to a correctly calibrated fuel injection set up, so there could be no argument that the one or the other wasn't working to peak, I would guarantee that the fuel injected engine would get better mileage, plus, it would have better response and be smoother to boot.

Jose :)
 
R

RootesRacer

Donation Time
Bill Blue said:
Jon, before ordering, consider this.

The "squirters" they are using on the TR6 are will fuel a 3.4 liter engine, there are two of them, so you have enough capacity to fuel a 6.8 liter engine. They are fueling a 2.5 engine, so they have 2.7 times the fuel delivery potential needed. You will be fueling a 1725 engine, so will have nearly 4 times the capacity needed.

This is a situation where bigger is not better. Fuel volume delivered by the injectors is not a smooth slope down to zero. Every time the TBI's fire, they deliver a minimum amount of fuel. I think this minimum is probably marginally okay for the 2.5, but greater than needed at low engine speed for a smaller engine. This causes the fuel loading problems for the MG's, not the different firing order.

If instead, two injectors for the GM multiport injected 2.8 four were used, I believe this problem would go away as they would be functioning within their design range.

But I am not an expert in this field, Jarrid is. This is a distillation of an exchange between he and I about a year ago when I was looking at the Zeniths. Better check with him before laying out the bucks.

Bill
Click to expand...

I havent looked into the injectors they are using, if they are port injectors or old TBI injectors.

The bottom line is that for a 100 BHP engine, you need appx 60 lbs per hour of fuel injectors, so you would want 2 qty 30 lbs/hr injectors.

Anything less would cause the injectors to hit 100% duty cycle at high RPMs, anything more will reduce (to a certain extent) the controllability of fuel, particularly at idle since the injector duty cycle will be smaller than desired.

For my first EFI 1725, I used 4 qty 19 lbs/hr port injectors, in a 4 phase multipoint. This was enough fuel for 140 BHP or so, but since the engine only produced 120 or so BHP the duty cycle was 80% max, which is an ideal margin for safety.

As for milage, EFI will give you fine tunability a carb will never give you, but a reasonably well tuned/jetted carb will perform similarly in the mileage department.
 
64beam

64beam

Donation Time
Hi Jose and Jarrid,

Thanks for the answering some of my questions/grey areas that I had. I understand that EFI is definately more tunable than carbies, what I could not understand was the the huge difference some people had gained (did'nt seem like a true comparison).

Regards, Robin.
 
R

rootesrefuge

Donation Time
The injectors they currently recommend are from GM 4cyl engines, 87-93 2.0,2.2, and 2.5. The fuel delivery should be pretty close, and with the adjustability of the Megasquirt and an adjustable fuel pressure regulator, it should be no problem to fine tune the system.

The Megasquirt box is inbound, as well as a universal inline TBI fuel pump. The TBI and TPS kits are ordered, just waiting for the shipping cost before finalizing the order. Then it'll be a question of building the wiring harness and collecting the necessary sensors.
 
sunalp

sunalp

Diamond Level Sponsor
EFI with sidedrafttbi.com

Please let us know how this turns out. This is really interesting and would like to know in the angle of the CD150's on the Alpine change the way it works. I know that the TR6 has them on pretty level. Sounds like something I'd like to try!
Cheers!
Steve
 
R

RootesRacer

Donation Time
I finally took the time to look sidedrafttbi.com over.

Sad level of details on the site, going to the site of the guy who used the GM ECU on the TR6 has better info, but I am sorry to say that this setup doesn't get my endorsement.

The TBI injectors that are used are junk, I've used them, they belong in the 80s with the carbs they replaced.

Each injector will likely flow significantly different fuel levels, particularly at idle.
They are also set to flow about 110 HP per injector, which means you have double the fuel you will probably need, which means that your injector pulse widths will be short, and fuel control will be not so good.

These are way old school injectors, and the only reason they work on the car they are designed for is because in that application, they use only 1 injector, and O2 closed loop feedback to allow for injector to injector flow variations.

Without cherry picking matched TBI injectors, one pair of cyls will get more fuel than the other. This will show on the plugs. Megasquirt doesn't have the ability to trim one injector phase from the other, so you are stuck with the injector to injector fuel difference.

Had they used port style injectors with a wide flow nozzle cap, the fuel control would have been better, and you could have gotten an off the shelf "calibrated" injector that would have flowed 50hp each of fuel. Injector to injector matching is something that is important on a multipoint setup, but TBI injectors do not have this requirement.
 
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