Club G40 Forum
Technical => Engine and Transmission => Topic started by: Justin14100 on October 02, 2010, 10:43:25 am
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While searching for more off boost power I think increacing CC's is te best way to go (any suggestion??) but as a student living off Asda pasta it's pretty hard to come up with the funds to get some forged pistons and a re-bore. If I locate a 1W crank (anyone got one?) is it just use it with G40 con rods? As it's going in for a rebuild I could swap the crank then. Would it change the compression ratio or just give more stroke / cc's??
Thanks!
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Compression ratio will be out as well as the pistons from the block. New set of pistons needed really.
If you want extra cylinder capacity on a budget, then have a look out for Tom's thread on here. He has used a 1391cc ABD engine with a little boost :)
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Ok so that won't work - anyone got any tips for getting more power off boost?
Working on getting a metal head gasket on the car during a rebuild and I'm half way through a batch of 51mm throttle bodys with porter t-prices. Just wanna know, does it turn into a n/a engine off boost - so port matching and 4-branches make a big difference off boost?
Thanks!
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hi mate ive got a 1308cc bottom end which has been lightern and balanced. the engine does need honing tho. pm me if you intrested..
thanks
darren
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;) Good ideas from Portugal !! ;)
I have done several projects with 1w crankshaft, using 75mm stock pistons worked in CNC Machine to stay with the same compression ratio of 8:1 up with 1398cc-
I'm currently working on a project with same 1w crankshaft, JE pistons 77mm with compression ratio of 9:1 making 1472cc. have oil injectors and calibrated flywheel. but unfortunately this is an expensive project, the first assembly may be a good option for those with less money offering a good quality product with the 75mm stock pistons..
See you ::)
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I have done several projects with 1w crankshaft, using 75mm stock pistons worked in CNC Machine to stay with the same compression ratio of 8:1 up with 1398cc-
Do you know the exact amount you had to machine off to get this? What were the results like? Do you know how much you would need to remove for a higher compression like 8.5:1 or 9:1?
Thanks!
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If you're willing to machine pistons, why not get an ABD like Tommo did and machine the pistons down in that? The engines are cheap as chips, and all you'd need to do was sort the pistons out.
There's no rare/pricey 1W crank to mess about sorting this way, and if/when it dies you've still got your original G40 motor to throw back in (or build up as a 1.5 1W long-term project).
To get sprightly performance off-boost you need to raise the compression ratio. The 9.3:1 CR you can get with metal HG and 77mm Accralite pistons is very nice off boost compared to a stock G40 - though does need careful mapping as it's very sensitive to ignition timing on boost.
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If you're willing to machine pistons, why not get an ABD like Tommo did and machine the pistons down in that? The engines are cheap as chips, and all you'd need to do was sort the pistons out.
There's no rare/pricey 1W crank to mess about sorting this way, and if/when it dies you've still got your original G40 motor to throw back in (or build up as a 1.5 1W long-term project).
To get sprightly performance off-boost you need to raise the compression ratio. The 9.3:1 CR you can get with metal HG and 77mm Accralite pistons is very nice off boost compared to a stock G40 - though does need careful mapping as it's very sensitive to ignition timing on boost.
So without slashing half my student loan on some new pistons and a rebore the best thing I could really do is the metal HG when a rebuild and just get a good n/a tune on it?
Will bare the ABD block in mind for long term future though. Other than compression ratio any other tips?
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the crankshaft of the ABD and 78.7 is the same thing to the first piston engines diesel.E with only 75 of the 1391 and 1W is 79.1 and the piston 75 1398.Ficam give here some pics of some machined pistons CNC.
[URL = http://img714.imageshack.us/i/dsc00230gc.jpg/ ] (http://img714.imageshack.us/img714/2456/dsc00230gc.th.jpg [/ IMG] [/ URL]
[URL=http://img714.imageshack.us/i/dsc00231qg.jpg/][IMG]http://img714.imageshack.us/img714/4020/dsc00231qg.th.jpg)[/URL]
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With the block ABD'll always have a high compression rate, I think to get a good mount you'll ever spend money on a custom chip, otherwise the power to melt a piston.
[img=http://img714.imageshack.us/img714/4020/dsc00231qg.th.jpg] (http://img714.imageshack.us/i/dsc00231qg.jpg/)
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What is the point of more power off boost?
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What is the point of more power off boost?
i spend a lot of time off boost as i commute to uni in it (70 miles 3 times a week) so need as much power off boost as i can get for economies! just got 38mpg but want more! 40 is my best!
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sorry .. liked to tell me what are 38mpg or 40 mpg ..?
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sorry .. liked to tell me what are 38mpg or 40 mpg ..?
mpg is fuel economy, in european terms:
38mpg = 6.2L/100km (16km/L)
40mpg = 5.9L/100km (17km/L)
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whenever I make changes to the G40's engine capacity, these are meant to think of driving pleasure in many horses on the road, doing usually about 9 or 10 litres/100km .. consumption of six litres/100km here we do with stock G40 with only one compressor preparation ..
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whenever I make changes to the G40's engine capacity, these are meant to think of driving pleasure in many horses on the road, doing usually about 9 or 10 litres/100km .. consumption of six litres/100km here we do with stock G40 with only one compressor preparation ..
sorry there was a calculation mistake
38mpg = 7.4 liters/100km
40mpg = 7 liters/100km.
i have a few modifications on the engine but not many, i always intend to keep the car as "usable" as i can when making any changes.
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I haven't seen less than 11lt/100km for too long now :'(
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It's time for new sensoooooors!!! :P :P :P
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I used my Polo daily for the best part of a month, and always managed at least 30mpg (9.4L/100km) per tank of fuel - even when driving it hard, including down the drag strip! The best I got was 41mpg (6.9L/100km) on the motorway. Not bad considering it's turbo'd and running 21psi of boost.
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I think if you are bothered that you are getting less than 40mpg you are driving the wrong car! One of the things I like about the G is that it relatively sips at its fuel for the performance you get. Even when I hammer mine I never get below 30mpg and I think thats really good.
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I think if you are bothered that you are getting less than 40mpg you are driving the wrong car! One of the things I like about the G is that it relatively sips at its fuel for the performance you get. Even when I hammer mine I never get below 30mpg and I think thats really good.
oh dont get me wrong - its just i need to get that kinda mpg to be able to afford to keep it for this year (last year at uni) but ive had the mpg real low at times when i was flush ;) high speed cruising, b road thrashing, track trips and 40 mpg economy runs. why own anything else?
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be cheaper to buy an old peugeot 306 HDI or something similar, drive that and garage the g40 for a while wouldn't it? Also keeps the miles off the g40 meaning it wont lose value or get worn out.
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You are looking for better efficiency rather than increased power. Increasing compression ratio slightly with the metal head gasket should help fuel economy. Using the standard G40 inlet manifold will be better than a wide bore GT one.
The most difference is down to driving style. I can get my Ibiza turbo over 40mpg average if I drive like a granny on a long run. Following lorries works really well. If I put my foot down up hill the short term mpg figure on the computer can drop to less than 5mpg. Get a boost gauge on the G40 if you haven't already got one. It's a good indication of how much fuel you are using.
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be cheaper to buy an old peugeot 306 HDI or something similar, drive that and garage the g40 for a while wouldn't it? Also keeps the miles off the g40 meaning it wont lose value or get worn out.
possibly, thought about running my old 1l fox again; saving miles on the G? not much point, its done 180k already so its due a rebuild (oh how long do oil pumps last?) so not really bothered much about the miles - have no intention to ever sell it unless i desperately need the money (ever) ;)
You are looking for better efficiency rather than increased power. Increasing compression ratio slightly with the metal head gasket should help fuel economy. Using the standard G40 inlet manifold will be better than a wide bore GT one.
Get a boost gauge on the G40 if you haven't already got one. It's a good indication of how much fuel you are using.
been toying with the idea of a G40 manifold - do you think it would make much difference? as in if it cost £30 would get get its money back in fuel? i wasnt sure it made a huge difference or not, not much experience with it!
boost gauge is a good idea yeah, been thinking of a TIM turbo guage cause its got the colours on it:
(http://thumbs3.ebaystatic.com/m/mCss1WI16_MM5jRR8HH718w/140.jpg)
so it kinda shows the economy with the colours (kinda ;))
thanks for the advice - just a good time to get it running real sweet i spose new sensors and cleaned injectors ect. 40mpg is really good for a G i know but if i can get it more without reducing power ill be a happy man!
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Did you ever swap your induction kit over for a standard air box? That would help with the mpg.
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Did you ever swap your induction kit over for a standard air box? That would help with the mpg.
Yeah I did a while ago - induction kit was back on for my nurburgring trip and the mpg was deffo worse with it on high speed cruising
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My induction kit isnt too bad, i can get between 300-350 miles on a tank.