SDS throttle body

lowemp · Post by **lowemp** » Thu Apr 28, 2005 7:37 pm

Jake,
I got the message from you about the jenvey TB's. I figured that with exchange rates cost would be prohibitive. I have a 60mm ford mustang TB which is too long. If I don't need the air bypass valve I can cut it down to fit. So, the question is, Do i need an air bypass with the sds system?
Just for clarity, this is for the 2615 going into my squareback.
thanks Jake,
Michael

cnavarro · Post by **cnavarro** » Thu Apr 28, 2005 7:47 pm

The air bypass is a very nice thing to have. It's possible to machine the throttle body down shorter like the unit that was attached to the plenum I sent to you, since that one was about an inch or two longer than it currently sits.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

lowemp · Post by **lowemp** » Thu Apr 28, 2005 7:58 pm

Thanks for the reply Charles.
I figured that the air bypass would be beneficial. The question that remains is if the SDS system is able to use it. I am assuming that normally in FI systems it has a valve actuator which is controlled by the "brain". If I am wrong and it is simply open all the time then I can still cut down the body and mount a bung in the intake hat which would connect by flexible hose to the plenum. Any insight would be helpful. I tried to answer this on the SDS site. But it's layout gives me a headache.

turbo_bob · Post by **turbo_bob** » Sat Apr 30, 2005 12:51 pm

lowemp wrote:Thanks for the reply Charles.
I figured that the air bypass would be beneficial. The question that remains is if the SDS system is able to use it. I am assuming that normally in FI systems it has a valve actuator which is controlled by the "brain". If I am wrong and it is simply open all the time then I can still cut down the body and mount a bung in the intake hat which would connect by flexible hose to the plenum.

Yes you need a air bypass valve for cold starting. The SDS only controls the on-off switching of the valve, it does not control a regulated idle speed.

vw_chuck · Post by **vw_chuck** » Sat Apr 30, 2005 2:51 pm

I've never used one. No point. If you have your values correct at idle then you don't need it. Especially with the new sds sytems that idle on the TPS values then shift up to the MAP values once you hit a certain TP value.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Sat Apr 30, 2005 5:09 pm

I am just getting to this portion of the SDS development and testing.. I do know that having the bypass is nice on start up but far from necessary. I can say this because this portion of the Kit Carlson system stopped working in my 912 after only a few thousand miles and it really did not impact cold start up at all....

Mike, lets talk this week. How is the plenum coming?

Sharkey · Post by **Sharkey** » Sat Apr 30, 2005 9:24 pm

An idle air control solenoid isn't required, but it does have its uses. It can be used to adjust airflow into the engine for higher idle speeds during cold weather opreration, add extra air during starting, and to compensate for parasidic loads such as A/C compressors. I'm running a Ford 5.0L TB due to the fact that it incorporates an IAC into the TB itself.

The SDS system will operate almost any solenoid-type IAC, but more advanced engine management systems are required to operate stepper-motor types.

turbo_bob · Post by **turbo_bob** » Sun May 01, 2005 11:50 am

vw_chuck wrote:I've never used one. No point. If you have your values correct at idle then you don't need it. Especially with the new sds sytems that idle on the TPS values then shift up to the MAP values once you hit a certain TP value.

Your talking EM-4 and I am talking EM-2, yes as Chuck said the TPS/MAP combo you dont need a bypass valve.
With my old unit I went a year without a bypass and it was rough, I had to stay in the car keeping the throttle cracked so the engine will not die out until the CHT warmed up.

lowemp · Post by **lowemp** » Sun May 01, 2005 7:55 pm

Thanks all ya'all for the input. (I spent 3 yrs in SC). Jake, I do need to talk to you about the plenum set up. give me a call any evening after 10pm your time. I will be pulling an all nighter tonight if you have the time. I am considering setting up this plenum so that you can adjust the runner length on the dyno. I have a few ideas on design but it might take an extra week or two. The Mustang TB might be too bulky. I am looking at a 60mm unit for a Mitsu eclipse made by modern performance. Check it out at
www.modernperformance.com/dcx/oneclipse.shtml
price is reasonable and it sure would look good!

Michael P. Lowe
'69 square awaiting a Nicked Raby 2615

Guest · Post by **Guest** » Mon May 02, 2005 4:51 am

A nice trick to fix stalling problems with cold engines and no bypass valve.

Set up a ignition map field at 500 rpm. Ie below your normal idle setting at circa 1000 rpm. At the 500 rpm site set the ignition with extra advance.

If the revs drop much below 1000 rpm the ecu advances the ignition and revs up the engine.

Its a great way of avoiding having the extra bypass gear (more to go wrong) .

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon May 02, 2005 7:07 am

Then there is always the possibility of the non computer controlled IAC... Thats just a manual switch on the dash that triggers the solenoid. I created one of these on my CIS injected bus for cold start ups and it works great and is only needed for maybe a minute or two in the mornings. Of course since it's CIS it creates a very lean mixture when it's in operation but it still works okay..

turbo_bob · Post by **turbo_bob** » Mon May 02, 2005 7:14 pm

MASSIVE TYPE IV wrote:non computer controlled IAC... Thats just a manual switch on the dash that triggers the solenoid. I created one of these on my CIS injected bus for cold start ups and it works great and is only needed for maybe a minute or two in the mornings. Of course since it's CIS it creates a very lean mixture when it's in operation but it still works okay..

Thats what I did, I used the rear window defroster switch and hooked it up to my solenoid, only needs to be on for about 1 mile of drive time. The MAP sensor compensates for the extra fuel.

lowemp · Post by **lowemp** » Mon May 02, 2005 7:25 pm

So, it appears that I can use a TB without consideration of the air bypass. If I want it later I can plumb one in from the pre TB intake pipe to the plenum and then set up the SDS to use it. Or if I do have a TB with an air bypass I can use it, or not. Since this will be a daily driver I am inclined to have it for initial warm up. While we are on the topic what are your thoughts on size of the TB for a 2615 with a redline at 6000? I am currently searching for a 60mm +/- 2mm.

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Mon May 02, 2005 7:35 pm

Mike, the 60mm sounds fine... Anything bigger than that and the throttle will be very touchy on your cruiser.... For you smaller would be better if you can't find exactly the 60mm size..

lowemp · Post by **lowemp** » Mon May 02, 2005 8:12 pm

Jake,
I am available if you have time to talk tonight. I have the parts for the plenum all over my desk trying to estimate volumes.

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