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choke and egr question with dutra duals
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Author:  DadTruck [ Sat Mar 26, 2011 6:37 pm ]
Post subject:  choke and egr question with dutra duals
working through the last stages of setting up the Dutra dual install and have a couple questions

1) is there any down side to not having any egr? This is for the D-150 and is intended to be a street-tow vehicle,, and I just like the looks of the twin dutra's more than the front Dutra combined with a hacked off stock manifold for the rear 3 cylinders,,but doesn't some egr actually reduce combustion temps and allow more advance at cruse?

2) for the carb, using a holey 2280,, for the choke,, used the search function and found the www.carbsonly.com electric choke kits,, one posting recommended the 1232 kit,, but said some custom choke pull off rod forming will be needed,, the posts were from 2006,, so is that still the best option or is there something else available?

thanks
Author:  ceej [ Sat Mar 26, 2011 6:48 pm ]
Post subject: 
The only concern is you won't want to have a bunch of partial throttle advance. For a tow rig, you aren't going to want a bunch anyway. Yank the vacuum advance off of it. You won't see any remarkable change when running heavy anyway. The only time the economy would be effected would be empty cruise at secondary access legal speeds, and then only a small amount.

Don't have anything with a choke on it. Couldn't speak to the other question. :wink:

CJ
Author:  4speed [ Sat Mar 26, 2011 6:50 pm ]
Post subject: 
I believe that the EGR lowers combustion temp and lowers NOX.
Author:  SlantSixDan [ Sat Mar 26, 2011 7:23 pm ]
Post subject: 
I would definitely use the half-a-stock-manifold for the rear three cylinders whether or not I wound up running EGR; without it you lose intake manifold heat, which is not just a winter/cold-weather thing. See here (and more detailed & pointed discussion here).

As for whether to keep EGR, it depends on how much effort you're willing to put into dialling-in the perfect advance curve on your distributor. If you don't want to futz with the distributor, run EGR. If you do wind up keeping EGR functional, you can update to a more advanced type that is a direct bolt-on. Standard #EGV490. This valve has a backpressure transducer that modulates vacuum to the EGR valve to match EGR flow rate better to the engine load. Takes a smaller bite out of driveability than the non-transducer type valve.

I don't agree with Ceej regarding the vacuum advance unless you always only ever drive this vehicle uphill towing a heavy load. If that is not the case, running without vacuum advance will mean pouring gasoline money right out the tailpipe, aside from the big bite it will take out of driveability. I would view disconnecting the vacuum advance as a quick and dirty temporary get-by deal until you get around to recurving the distributor properly.

It'll be important to pick your spark plugs carefully for this application. I don't know what the rest of your build looks like, but you will likely want to run plugs that are a couple notches colder than stock; that'll also help control pinging. So will waterless coolant; see here and follow the link in that post.
Author:  DadTruck [ Sun Mar 27, 2011 7:01 am ]
Post subject: 
thanks for the info on the EGV490,, I like the idea of some EGR,, as on a slant the egr is introduced into the intake at the base of the intake,,the section with the most area also will be the lowest pressure point, introducing warm gas there has to help with maintaining fuel vaporization.

on the choke question,, is the electric choke from carbsonly still the best choice?,,, I am not going to have a choke pocket as I am working up a plan to get EGR with a rear dutra.
Author:  SlantSixDan [ Sun Mar 27, 2011 9:38 am ]
Post subject: 
Still don't understand why you are rabid to have the Dutra rear casting. Doesn't sound like you're building a race motor. You planning on staring at the engine all day and all of the night...or driving the truck? :?:
Author:  ceej [ Sun Mar 27, 2011 10:43 am ]
Post subject: 
Some points to consider with the Dual Dutra Duals:

1. You will need to run a mini-starter to clear the rear pipe.
2. You will not have a provision for EGR.
(I think Dan misunderstood the question I was answering. EGR is a good thing. I only answered the part about not having any EGR.)
3. With dual headpipes, one of them very close to the brake master cylinder, you will want to come up with a way to knock the heat down. Take a look at photos of all the different head pipe configurations used with the Dual Dutra Duals. You will see that the rear pipe comes very close to the brake master, and is extremely close to the starter motor.
In the pickup you will have a bit more room to work with around the master cylinder. It's still right on top of the location for the rear head pipe.

I wrap the head pipes, and use a thermal shield to protect the starter.

If you run without the EGR, I'm going to put down a WAG that you will see a drop in fuel mileage of a mpg or so. (All other things being Equal) Due to the improved flow over a single, you may actually see an increase in MPG.)

Adjusting your vacuum pod to a minimal advance under cruise can make up for not having EGR, and you will want to adjust the mixture to match. EGT and cylinder head temperatures will increase without EGR. Be prepared for that. The best way to combat the heat is to decrease timing. Depending on compression and so forth, you should be able to run regular. Run whatever the lowest octane rating is that doesn't detonate. If you don't, more of the raw fuel will get blown out the exhaust port doing little to no work.

The Dual Dutra Duals are pretty, and flow a tad better than the modified rear, in my opinion. For a torque situation, I would stick with the modified rear, and limit head pipe size to 2" or perhaps even smaller. If you want rumpity power, not useful when towing, then 2" dual headpipes are pretty ideal.

3¢
CJ
Author:  DadTruck [ Sun Mar 27, 2011 2:55 pm ]
Post subject: 
SSD,,
for pure functionality you may be 100% right,, however there are are cases where function can follow form, where asthenics are part of the plan.
I like the look of the rear dutra,a lot more than a hacked exhaust manifold.
Now that we agree that egr and a warm intake are good things,, the questions is,,how else can that be done? I have an idea,, about bringing a duct off one branch of the down pipe to bring heat and egr up to the intake manifold base. For a 20th century fix to a cold intake ,, how about a spiral or grid heater in the intake tract. Neither of these remedys are complex,, we'll see how it goes.
Ceej,, agree 100% with the starter clearance issue,, don't know why Doc set it up so close,, but it is.
Thanks again for the input
Author:  Reed [ Mon Mar 28, 2011 11:05 am ]
Post subject: 
Quote:
SSD,,
for pure functionality you may be 100% right,, however there are are cases where function can follow form, where asthenics are part of the plan.
I like the look of the rear dutra,a lot more than a hacked exhaust manifold.
Now that we agree that egr and a warm intake are good things,, the questions is,,how else can that be done? I have an idea,, about bringing a duct off one branch of the down pipe to bring heat and egr up to the intake manifold base. For a 20th century fix to a cold intake ,, how about a spiral or grid heater in the intake tract. Neither of these remedys are complex,, we'll see how it goes.
Ceej,, agree 100% with the starter clearance issue,, don't know why Doc set it up so close,, but it is.
Thanks again for the input
This sounds like a great deal of work to achieve only a certain look. Using the factory exhaust manifold for the rear is a proven workable and easy solution. You should also be aware that the Carbs Only electric choke setup bolts to the factory choke pocket. You cannot use the Carbs Only choke setup with a rear Dutra manifold. I also recommend using the factory manifold.
Author:  Doc [ Mon Mar 28, 2011 11:48 am ]
Post subject: 
Quote:
...agree 100% with the starter clearance issue,, don't know why Doc set it up so close,, but it is.
The Dutra exhaust casting was designed to be used on the front 3 cylinders and we later "revised" it so it could be used on the rear.
Basically, this is a "work-around" solution... to avoid the expense of re-tooling to make a special rear casting.
Does it work... yes. Is it an 'optomized solution"? No.
DD
Author:  DadTruck [ Mon Mar 28, 2011 12:17 pm ]
Post subject: 
why would I need a choke pocket with an electric choke???my guess is that the electric choke mount bolts to the threaded holes in the existing pocket ,, but I bet I can make a little bracket, that would do as well,,

or is the electric choke also needing the heat sink of the stock manifold to function properly, per the guy at carbsonly he has seen the electric choke fastened to an intake manifold with a hose clamp, says it does not need radiant heat,,,

seems to me like it would work without a choke pocket

http://www.carbsonly.com/frames/carsandtrks.htm
Author:  wjajr [ Mon Mar 28, 2011 2:26 pm ]
Post subject: 
DadTruck:
or is the electric choke also needing the heat sink


That is the point of an electric choke, it creates its own heat to simulate engine coming up to operating temperature, at which point it is fully pulled off.

When headers are used there is no exhaust heat directed to bottom of carburetor, and intake manifold to help keep fuel in suspension. When fuel puddles on floor of manifold a lean mixture is created causing drivability issues, and sometimes carburetor icing will also take place.

This separation of fuel from air will subside as the engine warms up over several minutes, or longer if ambient air temperature is low. To overcome a lean mix, the choke has to be slower to open until engine & compartment warms enough to heat intake manifold.

Often an electric choke will pull off too soon on header equipped engines such as our slants where the carburetor is cantilevered out away from the engine in mid air. To slow down pull-off, a device that reads engine temperature, a thermistor, is installed in series on the ground side of the electric choke. What it dose is when cold, voltage is limited, and as engine warms the voltage increases across the bimetal spring, heating it, and causing the choke to open.

My engine was extremely cold blooded with just an electric choke. I added a thermistor which greatly improved cold start in summer, and temperatures above 50 degrees, but below 50 degrees she had drivability issues. At 35 degrees it was a stumbling, fuel sucking, non idling pig due to icing, and fuel separation.

Than I made a hydronicly heated hot spot under the carburetor, feed by heater loop coolant. Now the car always starts and runs well no mater how cold it is out, or humid.
Author:  ESP47 [ Mon Mar 28, 2011 3:10 pm ]
Post subject: 
I suppose you could mount the termistor on that hole on top of the head for lifting the engine. Then make a bracket to mount your choke on the other hole.

That'll work for your choke but your heat riser problem is another story.
Author:  DadTruck [ Mon Mar 28, 2011 4:18 pm ]
Post subject: 
wjajr
I did some searching on this forum and found another one of your posts under 'cold weather starting' where you mentioned the thermistor. I think you mentioned it was available through Holley,,, would you happen to have a part number or a resistance rating for one that is applicable?

thanks
Author:  wjajr [ Tue Mar 29, 2011 5:57 am ]
Post subject: 
Quote:
I think you mentioned it was available through Holley,,, would you happen to have a part number or a resistance rating for one that is applicable?


Dad Truck, funny you would ask. For some reason that particular part is hard for Summit & other vender’s search engines to locate, yesterday was no different as I intended to hot-link it, but could not dig it up. This morning I located it in my favorite’s list, because of it being such a PIA to find in the past, but due to Halfzimers, (half the time I’m out to lunch), had forgotten that I had saved it…

Bill
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