Menu toggle

Injectors

B

bluedexter

New member
Been looking at pics. of S2 engines and noticed that all the injectors seem to be colour coded green. As my S2 has light brown ones I was wondering if this might be significant or just dependant on the year?
As I have been having a few fuel related niggles could this be the cause?
Chris
 
Not 100 % but preety sure taht they are colour coded regarding fuel flow capacity.
 
I'm not sure either but I can sell you a pair of green ones for 40£ delivered if you want to try out the cheap way? Best of luck sorting the niggles ! Niels
 
ORIGINAL: bluedexter Been looking at pics. of S2 engines and noticed that all the injectors seem to be colour coded green. As my S2 has light brown ones I was wondering if this might be significant or just dependant on the year? As I have been having a few fuel related niggles could this be the cause? Chris
Click to expand...
I believe it is dependant on year or build run or somesuch as mine had brown ones, it may be a cause of an issue as I had mine swapped to green ones when I had the head rebuilt by EMC. Kevin muttered something about it not fueling quite right at the top end but as it didn't cost me much I didn't question it much. Its notable though that my race car now sounds different with the green injectors, rebuilt head and different chip (Evolution rather than Promax) but its difficult to say if that is actually anything to do with the different injectors.
 
I've done a little digging and discovered that the injectors fitted to my S2 are part no. 280 155 003, the correct part no. for the S2 is 280 150 811. Both have approx. the same delivery but the correct injector has an impedance of 2.4 ohms whereas the ones fitted (brown) have an impedance of 15.4 ohms. The effect of this is explained in this extract: High impedance injectors require relatively low drive current. Less heat is therefore generated in the drive circuits of the ECU, but the penalty is slow injector opening times. Low imedance injectors require much more drive current. Faster injector opening times, but more heat generated in ECU. Connecting low-impedance injectors to an ECU designed for high-impedance injectors would cause that ECU to switch greater injector drive currents than intended, and this can cause excessive junction temperatures in the driver transistors which equals smoke. Connecting high-impedance injectors to an ECU that expects low-impedance injectors can't do any damage electrically to the ECU or injectors. But how well it would work is another matter as the injectors are opening far slower than the ECU expects and so presumably your fuel delivery would be up the creek. More info here: http://www.witchhunter.com/injectorimpedance1.php4 I wonder how many other 944s there are around fitted with the wrong injectors? Chris
 
There's a green set on ebay at the moment, cant imagine who put them on but they are cheap [;)] [link=http://shop.ebay.co.uk/rsalmons0/m.html?_trksid=p4340.l2562]Link[/link] Rich
 
ORIGINAL: bluedexter I've done a little digging and discovered that the injectors fitted to my S2 are part no. 280 155 003, the correct part no. for the S2 is 280 150 811. Both have approx. the same delivery but the correct injector has an impedance of 2.4 ohms whereas the ones fitted (brown) have an impedance of 15.4 ohms. The effect of this is explained in this extract: High impedance injectors require relatively low drive current. Less heat is therefore generated in the drive circuits of the ECU, but the penalty is slow injector opening times. Low imedance injectors require much more drive current. Faster injector opening times, but more heat generated in ECU. Connecting low-impedance injectors to an ECU designed for high-impedance injectors would cause that ECU to switch greater injector drive currents than intended, and this can cause excessive junction temperatures in the driver transistors which equals smoke. Connecting high-impedance injectors to an ECU that expects low-impedance injectors can't do any damage electrically to the ECU or injectors. But how well it would work is another matter as the injectors are opening far slower than the ECU expects and so presumably your fuel delivery would be up the creek. More info here: [link=http://www.witchhunter.com/injectorimpedance1.php4]http://www.witchhunter.com/injectorimpedance1.php4[/link] I wonder how many other 944s there are around fitted with the wrong injectors? Chris
Click to expand...
Its the injector dead time that will screw things up here, the ECU looks at battery voltage and calculates how long the injectors take to open. So under cranking with 8V instead of 14V the injectors take longer to open. The ECU uses lookup tables for this so if you swap the injectors the values will be wrong. Swapping to high impedance probably means the engine will run lean as more of the time will be opening the injector and less delivering fuel than the ECU expects. This would probably be most noticable at low power as there is less fuel going in and the ratio of dead time to open time is higher.
 
Under the impression that my '91 S2 had been fitted with the wrong injectors (brown tops) I replaced them with the green topped ones, as listed in various manuals. The green injectors are very noisy but but the car runs ok. Not being happy with the noise I did some more digging and discovered this on the Rennlist forum; http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/205981-dme-differences-for-early-late-s2s.html The chap seems to know what he is writing about but before I revert to the originals can anyone verify this? Having only done 3 miles since changing I just hope that no damage has been done. Chris
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Back
Top