Club G40 Forum
Technical => Engine and Transmission => Topic started by: Pepe on August 23, 2014, 12:42:19 am
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Hi guys, just wanted to throw some ideas your way, I have a mk1 golf, 1.5 jb 70 bhp carb engine and as fun as it is I'm after abit more and I'm going to do the bay this winter so it's the perfect opportunity, my only issue is I walk around the show fields and really fancy something different to whacking in an abf/g60/20vt etc etc, so that got my creative mind wandering, so I remembered reading winston's g40 carb turbo thread and really love the simplicity and left field nature of it.
soooo (I bet you can see where this is going ;) ) I took to the drawing board, my engine is 8:2:1 compression ratio and the g40 is 8:0:1 so not a million miles away! And there's a massive void in the bay...
(http://i968.photobucket.com/albums/ae167/pepe1987_bucket/FC3319AF-B2E7-4A8B-81B1-BE1E78B04A8F_zpsdokmb5fs.jpg) (http://s968.photobucket.com/user/pepe1987_bucket/media/FC3319AF-B2E7-4A8B-81B1-BE1E78B04A8F_zpsdokmb5fs.jpg.html)
all being well what I want to do is use a completely bog standard g40 charger (I'm keeping cost down and not chasing figures etc just want to be abit different) I can use the twin port vacuum canister (a la kjet turbo) on my dizzy for ignition advance/retard, use a r5 gt turbo carb, take advantage of then V belt setup that is already running my alternator and waterpump abit of custom fab work to mount it, custom pipe work/inter cooler etc and have some fun with a relatively inexpensive engine, I have another one that a friend is letting me have so I've not got much to lose. But I have a few questions regarding the g40 g-lader that I hope you guys can help me with
1. if I cannot get a r5 carb for a reasonable price I'm going to have to use a different carb, so I would need to know what psi the g40 puts out?
2. Oil feed, does the g40 need one or is it like the m45 "lifetime" oil setup?
3. If it does need an oil feed, I'm guessing I take it from the sum, but where do I return it?
4. How much should I be paying for a standard g40 charger?
5. Any size restrictions on intercoolers etc
6. What sort of increase would it make, so I can plan brake conversions etc?
7. thoughts?
Cheers guys
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1. standard boost is 0.5 bar approx 7 psi on standard pulley.
2. G-lader needs an oil feed. This is picked up from the back of the cylinder head on the g40.
3. I dont know your engine at all, but the feed will most likely need to be picked up from the oil pressure sensor by way of an adapter. The return would be to the sump.
4. A standard charger depending on mileage and condition will be around £200
5. No real intercooler size restrictions, the standard coolers arnt particularly large and these can be picked up for around £20 second hand.
6. A standard polo gt is 75bhp. If your engine is 70 bhp and in good condition you might make as much as 113bhp. This is a total guess though, it would be interesting to see the outcome!
7. Give it a go. always good to see people doing different things. Im sure there are other considerations which people will mention.
Best of luck...
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If you can't find a r5 turbo carb I think Renault did a 1.7 carb turbo and am pretty certain that engine was shared with Volvo in there 440 and 480.
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Or this if you're quick, (ebay item number) 331290298865
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If you are looking for something out of the norm to do, why not using an m24 charger out of a newer vw! They are small and I think they can make up to 1bar. They don't require an oil feed or return, noone has done one before and you could probably make a drow through setup and use the standar carb. A blow through setup will make more power but a drow through is way easier to make since it doesn't require an intercooler or a blow off valve. The difference between the two shouldn't be more than 10hp. You could easily fit multi-v pullies out of 90's models vw and with some custom brackets it shouldn't be too hard. The standard G40 chargers are just too much maintenance in my opinion.
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I chose the g lader because of ease of use really, I has a v belt pulley so I can use my existing auxillary belt set up to power it! I want it to be as simple as it can be but work well
Great shout on the 1.7 turbo carb I'll look into that hopefully being a solex carb they will bolt on to my inlet with very little fuss like the r5 one does!
I'm pretty sure the mk2/3 polo uses a 1b3 carb as my 1.5 does so depending on my success it could be a good way for people to charge lower powered polos aswell
Thanks for the info so far guys!
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Well I wouldn't call it ease of use with a g lader. From my experience with those they are overpriced, mediocre on power and flow, hard to service and can blow to pieces for no apparent reason! Remember that you will still have to make the oil system for it, mount it with some custom brackets and the with the v belt setup you will still have to change the pulleys as the charger needs 2 of them to function properly. Its way easier to simply upgrade a couple of pulleys in my opinion and go with an eaton that requires no oil system or service but hey, it's your project not mine.
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You make some very good valid points there man, not really concerend myself with making anymore boost/power than a g40 as its still unexplored ground, but I will look into the physical size of the eaton chargers m24 would probably be best but I'll look non the less
with the pulley situation I suppose I could do it as I've got a few alternators from 6n/mk3 golf I've broken in the past so it would be a case of swapping the bottom v belt pulley on the water pump, and crank for the ribbed belt(don't know if that's possible? I also have an abd for parts that I could possibly scavenge off, a couple of close friends are fabricators and I was gonna get one of them to machine me a twin vbelt pulley and just swap the 1 pulley but maybe your right if I'm down there swapping pulleys it might pay off, they will be helping me mount it, weld in the oil feed to the sump etc my neighbour is a forklift mechanic and has everything I need for the lines etc so that wasn't a problem
Also I might be worth it to keep the period look but I will take myself back to the drawing board and see what else is available to convert the old big block the ribbed belt!
Cheers again I'm glad I came here some good ideas!
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You'll want an oil feed from the head, drain in the sump or back in the block.
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Yeah I'll take it from the piece where my vdo gauge sender and pressure switch are then replace the oil filter housing for a threaded one and move my oil pressure switch down to there, then weld on an inlet to the sump, what thread is the oil feed/return in the glader?
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m10x1mm
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Perfect cheers
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oil the drain is m10x1.
The feed is a fine pitched m8.
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what's m8? the fitting into the head is m10x1mm. The t-piece I have on mine is made with a brake pipe fitted brazed onto a drilled and tapped block of brass. Or am I misunderstanding something?
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The feed at the head us m10x1
The feed into the lader in the lader itself is m8fine.
The drain in the g lader is m10x1
The drain fitting on the block is m10x1
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Ah cool thanks for clarifying that!
My t piece WAS 2 male brake line connectors welded back to back then a t piece(3way female) off a mini, was ugly but worked a treat!
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yeah I was just talking about the fittings into the engine itself for the feed and drain.
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Ok folks so I've bought a refurbed charger with 0 miles since refurb, Anyone know where I can get a crank pulley for the g40?
Also is there any issues with running one longer belt running the water pump alternator, and one running the charger?
Or can I use one belt?
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I have a crank and alternator twin vee pullies oem.a few marks. 10 quid plus post
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Yeah please man that's great, they will be off to the powder coasters with a ton of other parts so that's no real issue!
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Ok folks so I've bought a refurbed charger with 0 miles since refurb, Anyone know where I can get a crank pulley for the g40?
Also is there any issues with running one longer belt running the water pump alternator, and one running the charger?
Or can I use one belt?
The reason they went with the twin v belt originally was to maximize friction (not the most effective setup to begin with). The belts will start slipping at high rpm or hard acceleration and you will experience a drop in power. Other than belt wear and power drop, I doubt you ll have a problem with just one belt. I would still suggest you go for 2 belts though. You could set one for the water pump, alternator and charger and one just for the crank and charger. One could tension via the charger and the other via the alternator. This way you could use different length belts. A general warning though, since we are talking about belts, avoid over-tightening the belts with any setup as the lader doesn't appreciate it.
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I would have gone single belt if I couldn't get the pulleys, PeteG40 you have pm also! I've swapped the absolute dog turd standard alt out for a 90a bosch one (from a rocco) and I've got an air ride setup waiting for my broken wrist to heal before I fit it so hopefully the twin V-belt setup will help out there, my only real concern with all this is the water pump but if I'm doing v-belt I think my buddy's are gonna be called upon for a customer waterpump pulley! but as you can see it looks fairly straight forward piece of engineering might even get away with it if we weld extra flange on to it so the belt runs round everything just keeping it all in check!
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so my charger turned up today its a completely bone stock refurbished charger, now ive offered it up in the engine bay and i think rather than make my own im going to try modify a standard g40 bracket to mount it and also i could do with a outlet dome/elbow if anyone has these parts let me know im keen to purchase them!
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I have an outlet dome - call it £25 posted with the 2 pullies?
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Quick one, I'm pretty sure the r5 carb Won't have a boost return feature so that will obviously be getting deleted on the charger, is it literally just a case of bolting a blanking plate on and giving it a squirt of the grease every now and again? (Mileage?), if I was to go for a secondary filter would I also need the spray grease?
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I think you will have issues running a charger in blow through with no pressure regulation or bypass mechanism.
If you ran the charger suck through (carb before charger) then it's dead easy as the carb just operates like normally aspirated. The throttle on the carb limits the air through the charger and the flow/pressure will go down when you close the throttle. Old Bentleys and MGs in the 1930's used this set up with a Rootes type charger driven off the front of the engine. Unfortunately I don't think the G40 charger would survive having the petrol air mix going through it.
Running blow through means the charger intake is effectively fully open all the time and it will try to flow maximum air into the manifold all the time. On a closed throttle in the carb the pressure will build up to the maximum the charger is capable of so you will end up with a high idle speed. I think it would be really hard to get a carb to run well like that; pressure will go down with increasing throttle rather than the other way round. You would need some sort of pressure regulator downstream of the charger to vent off excess pressure build up. A turbo on a R5 or Metro has the turbo bypass mechanism that limits the maximum pressure and a turbo doesn't do much unless the engine is at full throttle.
Unlike a turbo the G40 charger flows roughly the same (per revolution) at all engine revs. Its the inability of the engine to take in the air at the top end of the rev range that gives the peak boost levels. When the throttle is not wide open the G40 throttle body has a mechanical bypass valve that effectively makes it normally aspirated to prevent unwanted pressure build up. A stock G40 on standard 75mm pulley flows enough air for something like a 1.8 litre engine. If you attached a G40 to a 1.8 engine you would see no boost pressure. On a 2 litre engine it would be slower than normally aspirated. As you have a 1.5 you will see less than the normal boost in a 1.3 Polo. That's not a problem; I would expect a maximum of 4 or 5 PSI under full throttle which will give a significant performance boost and won't melt the engine.
One option is to enclose your existing carb in an airtight box (you could hide the whole thing under the existing air filter housing). You then pressurise the box with the G40 and a pressure regulator (flap acting against a spring). The complete carb would see the pressurised air so you just need to up the jet rather than use a special turbo carb. I think the early Lotus Esprit had this sort of set up.
Alternatively get a G40 bypass valve and link it up mechanically to the carb throttle cable. You then run normally aspirated until full throttle.
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He was just asking if he should blank the second inlet port on the charger! The G40 engine has a return that picks oil fumes and since he cant have that with the carburetor he was asking of what to do to keep the charger oiled.
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Ok you've raised some interesting points there. Just an idea I'm gonna throw your way as you seem to know your stuff.
would I be able to have a pipe going from charger to carb and then where it connects to the carb have a return back to the charger with a butterfly with a spring on it? I'm thinking that it will take the path of least resistance when the throttle is shut and then when it's open it's creating a vacuum anyway so will pull the butterfly shut and then be pulled through the carb
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The bypass on a G40 only goes back to the charger to limit the noise (like a recirculating dump valve). You can just vent any excess pressure to atmosphere. If you look at your G40 charger you will see the main and bypass inlets are exactly the same and connect into the same bit of the charger. (On the original G40 versions there was only one inlet and the bypass join was part of the rubber pipe.) The oil breather connection in the G40 bypass hose is mainly there for emissions reasons; it burns off the oil vapours rather than just venting them to atmosphere. A secondary effect is lubricating the charger a bit but I'm not convinced that's why VW did it. If you wanted you could attach your oil breather system to a blanking plate on the second G40 inlet. (It will currently connect to your airbox somewhere.) Probably better off just venting the breather to atmosphere and using a blanking plate on the second inlet. Then apply small amount of spray grease occasionally (others can advise on how much/how often).
I would go for a mechanical bypass valve linked to your carb cable and dump excess boost direct to atmosphere. This should be more reliable and will allow zero pressure off boost. The turbo carb is more likely to work OK like that. I think that a turbo carb needle is specially shaped to match the boost/flow characteristics of the car it was designed for.
In terms of making it work easily a BMW mini Eaton charger in suck through is less trouble (apart from the belts); also no oil feed to worry about.
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the r5gtt carb has been used a few time in supercharger builds and seems to work well,, im going to stick with the glader now as i have bought nearly everything i need charger wise, just need to modify the bracket to fit to the 1.5 engine, play around with pulleys (going to try use the same belt length as the g40 for ease and availablilty but if not longer ones wont be too hard to source), the oil feed return isnt a problem as ive bought an oil filter housing with an outlet so my t-piece will go in there with my oil pressure sensor and vdo twin pole sender and the feed for the charger will go directly in the side of the head. the return is as simple as taking the sump off marking it with an X and handing that and a fitting to my mate. i might just do that with the oil breather or i might plumb it into the carb as it is now see whats going to work best
that just leads me onto the fueling ive just contacted a guy (kris hughes) about his 1.0 eaton'd mk2 polo which uses the r5gtt carb and asked him what hes done to combat the high idle/carb pressurisation thing you mentioned and i am waiting to see what he says but i am thinking of taking the boost pipes over the drivers side so i can fab up something using the throttle cam and a butterfly 90 degrees to the carb butterfly so when the carb is full open the bypass is fully closed and vice versa
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I'm not convinced that the Kris Hughes guy ever got his 1043cc Eaton working properly. Everytime I saw photos or heard of it running it seemed to be with the Eaton spinning, but the engine still naturally aspirated. Would be interested to hear if he actually got it running properly in the end.
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its weird that hed do that isnt it? it seems fairly nippy for a 1.0 on the youtube vids but obviously you cant tell speed very well
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You could use a blow off valve instead of a mechanical bypass. It will work pretty much the same way if not better as they close sooner and faster than a mechanical would. You could get one cheap from a 1.8T engine as they are not too loud or chirpy. Also if you want to recirculate your fumes just connect them to the inlet of the charger although they will lean your mixture a bit. As for the carb I didn't exactly understand what your fueling problems are. I imagine with the r5 carb all that would be needed is a pressure regulator.
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i did think of that but wasnt sure it would work without using the vacuum port on it, i thought about plumbing it in to the piston side of a bov with a spring rated to the correct pressure, then when it exceeded that pressure it would exhaust through the normal inlet side in a sort of back to front manner, when you say it will lean the mixture, how will it make the mixture to lean?
sorry by fuelling i meant tuning, high idle speed etc due to this bypass valve stuff
just researched r5 carb and it looks like i can use the dizzy vac lines to open the bov happy days!
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Not "too lean", just a bit leaner! You are burning fumes along with the gas/air mixture. If the engine can suck X amount of gas and air per revolution, a percentage of that X is fumes, thus less gas/air mixture, that is what I mean with leaner mixture. I am just saying you can probably get a cleaner mixture by venting them to the air via a filtered collector tank and be done with it.
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ahh you mean recirculating from the oil breather i understand now i thought you were talking purely air fuel ratio, i will keep my eyes peeled for a bov with a 6/7 psi spring or bypass valve depending on what turns up first and give that a whirl
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anyone know how much air the g40 charger flows per revolution? cannot find out?
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566cm³ per revolution. Rated speed is 10,350rpm.
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Brilliant thanks, What's the pulley ratio. And if anyone knows the ratios of the smaller pulleys that would be great also
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Still looking for some standard g40 crank and alternator pulleys!