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2.5pi efi conversion injectors

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Hi I have posted this on another forum but have got no response yet. So trying here.

I am currently working on a efi conversion for my 1973 triumph 2.5pi and need to get some injectors. I was wondering if anyone on here would know if the injectors in the link below would be suitable for my project? (I can get them at a much lower price). I know they will have enough flow. But I I'm not sure about if the extended nose is an issue.

Just a little extra info on my project to give people a background so they can make recommendations.

To hold the electronic injectors, i am going to use the original Lucas pi throttle bodies drill the existing injector holes out to the 13.5/14mm and strip the butterflies and block off any holes. Having a single throttle body on the end of the plenium tank. The throttle body I have is an 80mm one I got off eBay but from previous reading it may be. A bit large to get reliable performance down low. If it doesn't work well I will replace it. The ecu I am going to use will be an exumatsers emu classic with full sequential fuel injection. And either use a msd 6al2+stripped distributor for the spark being controlled from the ecu. Or also fully sequential spark.

Once the efi has been completed I have a Eaton m62 super charger that I will fit to the engine with forged pistons and a couple new pullies to convert to a 6 rib serpentine belt. I also have a. Lower compression head from a 2500tc that I was considering using.

Thanks for any help people around here can provide.

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Hello and welcome.

Interesting project. Several on here have converted 2.5s to EFI using the original manifold if, though I’m not aware of anyone adding a supercharger.

We do have a supercharged TR6 owner/builder on here but that uses a single 2”SU iirc.

Years ago in the USA a guy named Steve Downing (or Downey?) built a supercharged 2.5GT6 using an M62 and programmable FI. Whether there is anything left on the web about it I don’t know.

On your injector question, the ones shown don’t look like a natural choice, though given that some machining will have to be done whatever, most things are possible.  What is most important is that you have enough length to get the tip close to the runner without having to hack large chunks out of the casting to clear the connector.

Looking at the general shape of them, I wonder if you’ll need to machine the manifold at all - more a case of making plastic adapters in the style of the originals.

The flow looks on the high side also. The bottom end of the 2.5 won’t take anything like 300 bhp.

IMO the easiest ones to fit are from the EV1 style, which are fitted as you describe. I used the dark blue ones from the GM 2.5/3.0 V6 but there are many other possibilities.

Something else to consider with forced induction is that the factory plenum won’t hold much (if any) pressure and getting the rubber links to stay on and leak-tight is a challenge even NA!

my PI conversion her

plus Carl Nicholson’s here

Plus James Carruthers here

There are others too - use the search function and take a look around.

Andy Thompson (2fast2race) in WA has done one too and there are a couple of Oz based GT6 conversions from Craig (GT6Mk3) and 

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5 hours ago, JohnD said:

PeterC, of this parish, has a Wordpress page about his supercharged TR6 (and much else) at http://supertrarged.wordpress.com/

And TimD on the TRR site has fitted the M62 kit with a Holley carb.

The kit is NLA.

The Patton supercharged, inter-cooled and injected TR6 is impressiive: but my links are dead.

Beware, if an injector goes lean the piston will hole in a very few seconds under boost.



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Thanks all good responses so far. @Nick Jones with the injectors I was also thinking they have the extended tip so may work. I didn't think about making an extra plastic adaptor which could be easily done with a 3d printer. If that worked it would save me having to machine the manifold as you mentioned. I might get one of the injectors and see what I can work out. The flow is a bit on the high side but I'll see if I can find a better suited one. I was going to try and aim for around 200-250bhp once the super charger is fitted. But from what I read the forced induction will need higher flow injectors at the same HP.

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I saw that the injectors were showing as lower flow with forced induction, but I’m not understanding why. Obviously with forced induction they are injected against higher pressure, but normally the fuel pressure regulator reference port would be connected to the manifold and automatically correct for that so the differential pressure across the injectors is maintained……

200 - 250 bhp from the Triumph 6 is going to need some very careful building and some special parts in order to stop it eating itself.

I guess you are aware of Greg Tunstall in Ormiston?

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Although I take it over to Greg far less than I should. The amount I drive it at the moment is very low and ends up with the fuel seal on the metering unit perishing so it is then off the road longer while it is fixed. Has happened 2-3 times now. That is part of the reason why I'm trying out the EFI.

I do know of a few things I want to do to the car before I put the super charger in. Like forged pistons and rods. Roller rockers, Lower compression head from a parts 2500tc I have. And I also seen a skyline diff that from what I read is more reliable. Not sure how reliable the info is though.

Problem being all those things cost probably more than the car itself. But the car is a passion of mine and gives me something to do. So I will persist and try to achieve some good results.

If you have any other suggestions I'm open to and appreciate learning anything useful to the project.

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  • 1 year later...

Roller rockers are of limited benefit in terms of power boost on a forced induction engine where you won't be needing a wild, Hugh revving cam.

Forged pistons are expensive but steel rods relatively cheap. The Maxpeeding rods are, if anything over specced. Come with ARP bolts. The overspecification means the 'H' can be a bit wide and catch on the lower end of the bore (beyond the swept area) unless overbored. A bit of work with a die grinder can soon resolve this.

Steel cranks are mega bucks but the loadings from a low revving supercharged engine are different to a manually aspirated 2.5 revving engine are different in nature.

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