Fuel injection on a 1.3 (GF code)

I'm thinking about fitting single point fuel injection to my mk1 Driver by using parts from a mk3 Polo

Only thing I'm "worried" about is the lower compression ratio of my engine compared to the Polo engine

Any thoughts???

I wouldn't have thought the compression would make any difference :? The injection system will adjust itself to fuel the engine as best as possible.  The only affect the lower compression will have is that it won't burn the fuel as effectively, but that won't cause any damage, just means it might not be as economical as it could be!

But in all honesty I doubt you'd notice any difference between the two compression ratios

seriously dont bother, spi setup is pants and not any better than a good weber. if you're going to do it go mpi

but yeah dont worry about the compression it should be fine. in fact im pretty sure CR is same on GF and MK3 polo 1.3, the power is the same. its only the GT that has higher compression and that is MPI

rubjonny said

 in fact im pretty sure CR is same on GF and MK3 polo 1.3, the power is the same. its only the GT that has higher compression and that is MPI

The GF is 10.0:1 with flat top pistons.
The 3F is 10.0:1 with bowled pistons and valve cut-outs. (polo GT MPI)

The MH is 9.5:1 (average later mk2 polo hydro engine).

I just fitted a polo 3F engine in my Mk1 with an MH inlet manifold and a Weber 32/34 DMTL out of a scirocco. Had to use a scirocco header tank with a mk3 polo thermostat housing and mk3 polo radiator with the 1.1 golf switch and fan. Its using the later flywheel, clutch and release bearing on the original 3D 4 speed box from the formel E. Idles sweet as a nut, had a firing issue above 3K, but on inspection im putting it down to a knackered rotor arm. Yet to try it down the road since, but it runs sweet on idle and when revved.

Personally i'd ditch the early meccy lump in favour of the hydro engine, if going injection. The inlets on the early engines have random pre-heat ports. The inlet and exhaust ports do physically match up on both types though.

So to conclude your GF "driver" engine has the same cr as the polo GT MPI engine.

what about the AAV lump, is that same as 3F or MH? also how is it the GT has so much more power than the 3F if the CR is the same, all in the cam?

Polo_anorak said

rubjonny said

 in fact im pretty sure CR is same on GF and MK3 polo 1.3, the power is the same. its only the GT that has higher compression and that is MPI

The GF is 10.0:1 with flat top pistons.
The 3F is 10.0:1 with bowled pistons and valve cut-outs. (polo GT MPI)

The MH is 9.5:1 (average later mk2 polo hydro engine).
.

Pretty sure thats incorrect matey, the compression ration is 8.2:1 on a GF.


All the later hydro engines ran a higher compression ratio, probably because they had better fuelling systems than the carb engines.


I fitted Polo GT injection onto my HH engine (identical to the GF) and I'm loving it 8) A couple of die hard polo lads have commented on how nippy it is, and considering it doesn't have the GT cam, gearbox and compression its quite impressive

The only aspect of fitting this injection to an early engine is you'll have to swap the cooling system for the polo too.  Because you need the polo's water temp senders, you need the polo's thermostat housing. And it you have the polo thermo housing then you need all the corresponding pipework and have it routed the right way.

I managed to keep the GF/HH thermostat housing and made my own housing for the temp sender which I then welded on, but unless you have access to a lathe and an alloy welder then its not the best option.

Apart from that its very simple, wire in the fuel pump and ECU relays and the rest is self contained pretty much 8)

rubjonny said

what about the AAV lump, is that same as 3F or MH? also how is it the GT has so much more power than the 3F if the CR is the same, all in the cam?

AAV is the 1.3 SPI lump from mk2f polo's.

3F is the GT engine. 75 hp  comes from having MPI I guess, the cam profiles are probably more agressive than the other engines.

If you meant why does the 3F have so much more power than the GF driver engine? Then i'd put that down to the injection and the GF having a shit weber solex carb. Also the cam proflie on the GF is probably suitable lame.

cool just wasnt sure im not a polo/small block expert.

with the sensor issue does the old mk1 housign have an m10 or m14 thread? if so you can use early mk2 digi (m14) or abf (m10) ecu temp sensor. direct fit and will work with polo spi/mpi ecu

Phataz1 said

Polo_anorak said

rubjonny said

 in fact im pretty sure CR is same on GF and MK3 polo 1.3, the power is the same. its only the GT that has higher compression and that is MPI

The GF is 10.0:1 with flat top pistons.
The 3F is 10.0:1 with bowled pistons and valve cut-outs. (polo GT MPI)

The MH is 9.5:1 (average later mk2 polo hydro engine).
.

Pretty sure thats incorrect matey, the compression ration is 8.2:1 on a GF.


All the later hydro engines ran a higher compression ratio, probably because they had better fuelling systems than the carb engines.

I'd put money on the GF compression ratio being 10.0:1. I dont have a mk1 golf haynes to hand though. Your HH lump was 8.2:1 which is almost lower than my G40's compression at 8.0:1!

Here's a handy table courtesy of Gaz on clubpolo.

rubjonny said

cool just wasnt sure im not a polo/small block expert.

with the sensor issue does the old mk1 housign have an m10 or m14 thread? if so you can use early mk2 digi (m14) or abf (m10) ecu temp sensor. direct fit and will work with polo spi/mpi ecu

I'm not sure what thread the mk1 housing has for the sensor but its a single pole sensor, and the polo 3F sensor has two poles but it isn't threaded. They are held in the housing with clips and sealed with an O ring so I'm not sure which other sensors might fit :dontknow:


The 3F engine has more power than the other polo engines mainly because of the cam and the injection.  The cam has much more aggressive lift and duration, like visibly obvious differences when you look at it All the other aspects of the GT engine like the gearbox/compression etc all help to create a well set up little car, but they make minimal differences if they are absent 8)

The GF cam is actually the best factory cam you can get for the early engines, and is near enough the equivalent of the GT cam but suited to the design of the mechy head engines :wink:

Just re-read what you said Rubjonny, so you're saying the ABF temp sensor (blue one?) has an M10 thread which fits the plug on the 3F loom?  If so, then that could solve the issue!  8)


Yeah Mr Anorak Sir, its been sopken about on Club Polo about how suitable the HH/GF engines are for forced induction due to the low compression ratio, but I think the general consensus was that they just aren't very strong engines so its not a great idea Thats why I gathered that the GF had the same ratio as the HH… I'm happy to be proved wrong though

Polo_anorak said

I'd put money on the GF compression ratio being 10.0:1.

I'm afraid I'll have to take your money fella I just check my Haynes and it says 8.2:1. Paypal is fine with me

the threaded digi and abf sensors are white but yeah, they plug in and work with the polo ecu as the white dig/abf and blue polo/mk2 digi ecu senders are all the same rating.

basically it depends what holes the housing has got! obv one of them is taken up by the dash sender. im just not sure how the mk1 smallblock thermoswitches are fitted, if indeed they have any! the early big block carb mk1 thermoswitches are in a dody inline bracket thing

my post above about the cr was based on ETKA showing the GF and AAV lumps both having the same power, so i assumed CR was the same seeeee.

Phataz1 said

Polo_anorak said

I'd put money on the GF compression ratio being 10.0:1.

I'm afraid I'll have to take your money fella I just check my Haynes and it says 8.2:1. Paypal is fine with me

Aaah! Fail. Dunno where I got that idea then :roll:

Would you accept chocolate coins?

Polo_anorak said

Phataz1 said

Polo_anorak said

I'd put money on the GF compression ratio being 10.0:1.

I'm afraid I'll have to take your money fella I just check my Haynes and it says 8.2:1. Paypal is fine with me

Aaah! Fail. Dunno where I got that idea then :roll:

Would you accept chocolate coins?

  Sounds good to me!




Rubjonny you once again surpass your reputation for being a legend! 8) The mk1 thermo housing has one threaded hole which I think is M10, and that is where the single pole sensor for the dash normally fits.  But it wouldn't be very difficult to just drill another hole and thread it to suit either of those sensors you mentioned! Saves all the crap that I did to fit the polo sensor  :roll:


You can just see the little single pole sender on the upper face of the housing here, with the boss I made for the polo switch facing the camera:

the advantage with your way is the blue sender is cheap