Alex Posted February 17, 2002 Share Posted February 17, 2002 When replacing injectors do I need any of these things, the web site I found these HKS parts on was unclear as to whether these parts are required for a Supra. Injector Grommet Injector Insulator Injector O-Ring Also a replacement fuel rail is needed but what else, other than possibly a pump, would and could be changed to make sure the fueling is never an issue??? I'm thinking of going for the GReddy Injectors as they are "only" $122 each which is a lot less than the HKS or Blitz equivalenets and the 720's cost as much as the 550's and 680's bizarrely..... Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted February 17, 2002 Share Posted February 17, 2002 You will need all of those, which particular items depends on which type of injectors you choose. They should all be fitted as new when you fit new injectors. A replacement fuel rail may be needed depending on which injectors you go for. The MKIV Supra as standard uses side fed injectors where as some aftermarket ones are top feed. You will also need an aftermarket fuel pressure regulator if you are replacing the rail. IMHO you do not want to skimp with any of the fuel fixtures and fittings, because one small leak could be a disaster. Quote Link to comment Share on other sites More sharing options...
Alex Posted February 17, 2002 Author Share Posted February 17, 2002 Cheers Martin, Do you mean that these parts come with new injectors or will have to be bought??? Is it a case of asking before ordering?? Is there a fuel pressure regulator which is well known for being top quality and VFM??? What size of pump is needed for 720's to make sure I never need to upgrade it on those injectors Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted February 17, 2002 Share Posted February 17, 2002 They generally come seperate, i think for the head end you could probably use the OEM ones, but best check with the supplier when you decide which injectors you are going to use. A lot of the American guys tend to use a Paxton fuel regulator, but i'm sure there are others that are as good, maybe CW knows of a decent brand and supplier. You can't really choose a pump alone on the size of injectors chosen you also need to work out what your maximum boost pressure is likely to be so that you can workout what the maximum pressure you'll require in the rail is. This will also have a bearing on a suitable fuel pressure regulator. We seem to be coming back to that old conversation of pressure and flow If you want to design a system piece by piece then there are a few factors to take into account (not masses), if you want to go for an off the shelf system (say PHR) then this should all of been done for you. You may want to take a look at this site :- http://supra400hptt.homestead.com/Fuel.html Particularly the attachments. The guy did it piece by piece but ended up with something close to an off the shelf system and saved a few $100 as well. This site has good info on different pumps, including the stock Supra one :- http://www.geocities.com/lutransys/jlucius2/j2-2-fuelpumpguide.htm (Edited by Martin F at 11:44 pm on Feb. 17, 2002) Quote Link to comment Share on other sites More sharing options...
Alex Posted February 18, 2002 Author Share Posted February 18, 2002 Thanks Martin Quote Link to comment Share on other sites More sharing options...
Alex Posted February 18, 2002 Author Share Posted February 18, 2002 Just found this http://www.roadraceengineering.com/fuelpumpflowrates.htm Left me with 3 questions Our car run at 12V's don't they??? How many amps are supplied to the fuel pump in stock form?? How could I turn up the ampage??? Then I looked at this.....brilliant injector worksheet http://www.rceng.com/technical.htm (Edited by Alex Holdroyd at 8:48 pm on Feb. 18, 2002) Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted February 18, 2002 Share Posted February 18, 2002 Supra's as stock use a switched 9v/12v system, increasing the voltage and hence the flow when the need is required. There is a simple mod somewhere on MKIV.com to keep this at 12v all the time, although what advantage this will give you in the real world i don't know. The Supra pump is one of the juiciest out there when it comes to current consumption, which makes any upgrades quite easy as you generally don't need to upgrade cabling. You can't turn up 'ampage' only voltage. The pump will draw as much current as it needs or to the limit of the supply, whatever comes first. I think some of the Americans have experimented with turning up the voltage further, but i don't think the results were that great. Quote Link to comment Share on other sites More sharing options...
GavinL Posted February 18, 2002 Share Posted February 18, 2002 Quote: from Alex Holdroyd on 8:37 pm on Feb. 18, 2002[br] Then I looked at this.....brilliant injector worksheet http://www.rceng.com/technical.htm (Edited by Alex Holdroyd at 8:48 pm on Feb. 18, 2002) Remeber this is US horsepower so it won't really workover here without a bit of adjustment. By the way, has anyone priced up the 550cc injectors etc from Toyota. Sorry to be boring and all that but it does work rather well and free from pitfalls. Quote Link to comment Share on other sites More sharing options...
Alex Posted February 18, 2002 Author Share Posted February 18, 2002 Quote: from GavinL on 9:07 pm on Feb. 18, 2002[br]Quote: from Alex Holdroyd on 8:37 pm on Feb. 18, 2002[br] Then I looked at this.....brilliant injector worksheet http://www.rceng.com/technical.htm (Edited by Alex Holdroyd at 8:48 pm on Feb. 18, 2002) Remeber this is US horsepower so it won't really workover here without a bit of adjustment. By the way, has anyone priced up the 550cc injectors etc from Toyota. Sorry to be boring and all that but it does work rather well and free from pitfalls. Errr...not me ---- a blindingly obvious oversight. :biggrin: Having spent the last hour dribbling over the PHR/SP fuel system kits I'm starting to realise just what a phenominal task it is to do it properly. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 19, 2002 Share Posted February 19, 2002 The 550's are a known quantity, I agree with GavinL For a measly 600odd- quid I can sort mine out. Shame I haven't got that for the near future - how frustrating... I am working my way towards a credit card based f***-it moment... -Ian Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 19, 2002 Share Posted February 19, 2002 Quote: from Alex Holdroyd on 9:18 pm on Feb. 18, 2002[br]Quote: from GavinL on 9:07 pm on Feb. 18, 2002[br]Quote: from Alex Holdroyd on 8:37 pm on Feb. 18, 2002[br] Then I looked at this.....brilliant injector worksheet http://www.rceng.com/technical.htm (Edited by Alex Holdroyd at 8:48 pm on Feb. 18, 2002) Remeber this is US horsepower so it won't really workover here without a bit of adjustment. By the way, has anyone priced up the 550cc injectors etc from Toyota. Sorry to be boring and all that but it does work rather well and free from pitfalls. Errr...not me ---- a blindingly obvious oversight. :biggrin: Having spent the last hour dribbling over the PHR/SP fuel system kits I'm starting to realise just what a phenominal task it is to do it properly. OHH GOD, not the different HP thing again :-( I can get you a massive in tank pump if you want, the sort they use on the serious Skylines. It will be cheaper to get all the injectors and rail as a package from a used UK / US car. Be very careful with mixing and matching stuff unless you want to have to start getting fuel rails made. The one on my RX took me 2 days to do, and you don't want to be into those sort of machining costs. Also be aware of different injector impedances and feed ports. Bosch do a nice 5 bar adjustable fuel pressure reg, but if you go custom you can easliy blow 300 quid on Aeroquip type fittings if you don't want Jubilee clips everywhere. These fuel system jobs can and will snowball if you move away from stock type parts. Quote Link to comment Share on other sites More sharing options...
Alex Posted February 20, 2002 Author Share Posted February 20, 2002 Is it true that you can bore out the 550cc injectors??? Is it safe to do so? Is it a "black art"?? Can you use an uprated fuel rail and pump to increase the flow of the injectors? Ie if I get 550's and then whack on an HKS/PHR rail will I be better off then a 550cc and stock rail??? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted February 20, 2002 Share Posted February 20, 2002 All this talk of "uprated rails" is BS, look at he bore of the feed pipes. if the rail bore is bigger, then changing to a bigger bore is pointless. Given that injectors are available stock, off the shelf, in higher flow volumes it is a bit pointless risking boring out lesser flow units. The usual reason for changing injector rails is a change from end feed to side feed, or vice versa. Quote Link to comment Share on other sites More sharing options...
Alex Posted February 21, 2002 Author Share Posted February 21, 2002 Thanks Chris, just checking I had everything covered Quote Link to comment Share on other sites More sharing options...
Guest Terry S Posted February 22, 2002 Share Posted February 22, 2002 Alex, 1/. The 550's won't fit the HKS Fuel Rail 2/. As Chris said you would need to increase the size of the line or no. of lines from the pump/s to make any real use of the fuel rail 3/. Dependant on the HP goals the stock pump will only flow so much fuel ( UK pumps flow mor the J- Spec) 4/. How much bhp you are after determines the size of the injectors 5/. The ability to control larger injectors must be looked at. 6/. Fuel pressure also comes into play when sizing the injectors, & the volume on stock pumps drops of dramatically above 50 psi Quote Link to comment Share on other sites More sharing options...
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