Stock injectors too large??

For discussing injector selection,manifold modifications, throttle bodies, fuel supply system design and construction, and FIdle valves and IACs.
Forum rules
Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.

If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).

If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days

The full forum rules are here: Forum Rules, be sure to read them all regularly.
Post Reply
Tony H
MegaSquirt Newbie
Posts: 6
Joined: Tue Aug 04, 2009 10:10 am

Stock injectors too large??

Post by Tony H »

I am planning to MS my 1971 Mercedes 3.5L V8 coupe (213 CID) with existing Bosch D-Jetronic. Researching the stock injectors (Bosch 0280150034) they flow 338 cc/min which seem to be almost twice the size needed for a 230HP engine. Is my thinking correct? They are also low impedance injectors. My questions are:
Should I install smaller Hi Z injectors? Would smaller injectors make tuning easier?
If I use other injectors I would like to use injectors that will directly replace my existing injectors. How could I research this? They use hose and clamp connections. I want to modify my car as little as possible because it is a collectible model.
Thanks
Tony
Bernard Fife
Master Squirter
Posts: 475
Joined: Thu Oct 29, 2009 12:54 pm

Re: Stock injectors too large??

Post by Bernard Fife »

Tony,

Whether the injectors are too large depends partly on whether you use MS-I or MS-II. MS-II has much more injector pulse width resolution, which helps avoid the idle pulse width problems created by large injectors (http://www.megamanual.com/v22manual/mtune.htm#idlepw).

If you are going to control the ignition timing too, you will need MS-II anyhow. If this was mine, I would keep your current injectors and use MS-II.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it.” - George Bernard Shaw
Tony H
MegaSquirt Newbie
Posts: 6
Joined: Tue Aug 04, 2009 10:10 am

Re: Stock injectors too large??

Post by Tony H »

Thanks for your reply Lance. I am planning on installing EDIS as part of my installation and have had a custom toothed crank wheel fabricated and have all parts.
One reason I was considering using different injectors is that the injectors for my car are rare and expensive and also to preserve my original injectors so I can make the car original if I ever sell it. I spent a little time researching injectors and I found some Mustang 19Lbs injectors that may be ideal. I know others have used Mustang inectors on similar installations. I would need to adapt the fuel connection to my fuel rail since my existing injectors use hose/clamp connections. I have a spare fuel rail I could modify. My car is dissasembled undergoing restoration so it will be awhile before it all comes together.
Look forward to realizing my engines full potential with a modern ignition and fuel system.
Tony H
MegaSquirt Newbie
Posts: 6
Joined: Tue Aug 04, 2009 10:10 am

Re: Stock injectors too large??

Post by Tony H »

After examining the Ford injectors I have found them to be identical to my original injectors with the exception of the pintle cap and the fuel connection. I can build a custom fuel rail-it is preferable to the hose and clamp connections the original injectors use. I removed a pintle cap from one of my original injectors and one of the ford injectors and the pintle is identical so it seems I can install the D-jetronic pintle caps on the Ford injectors and use the seals intended for the D-jet injectors. I have read conflicting information concerning the pressure regulator. Do I need a vacuum controlled regulator or can I use the original reg? I would like to keep as much of the original fuel delivery system as possible.
Thanks
trakkies
Super Squirter
Posts: 1162
Joined: Tue Dec 30, 2008 3:06 am
Location: SW London, UK

Re: Stock injectors too large??

Post by trakkies »

Tony H wrote:After examining the Ford injectors I have found them to be identical to my original injectors with the exception of the pintle cap and the fuel connection. I can build a custom fuel rail-it is preferable to the hose and clamp connections the original injectors use. I removed a pintle cap from one of my original injectors and one of the ford injectors and the pintle is identical so it seems I can install the D-jetronic pintle caps on the Ford injectors and use the seals intended for the D-jet injectors. I have read conflicting information concerning the pressure regulator. Do I need a vacuum controlled regulator or can I use the original reg? I would like to keep as much of the original fuel delivery system as possible.
Thanks
Not much wrong with the hose and clamp connectors - mine are 25 years and some 180,000 miles old. ;-) But later steel pipes can look better.
Are you saying there is no vacuum controlled fuel regulator? That's most unusual.
Dave P, London UK.
Rover V-8
MSII V3
EDIS
Tech Edge Wideband
Post Reply