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Author:  G15B [ Thu Nov 13, 2008 11:36 am ]
Post subject:  G15A CONVERSION

Hi, I finally got all my stuff together and finished my swap, here are the specs and mods and I will be glad to give you any info about how, what, who, and most important, how much.

- G15A block
- Honda P29 pistons 75.5mm
- G13B Dohc head ported & polished
- Honda D13 25mm exhaust valves (stock are 24mm)
- Honda D16 30mm intake valves (stock are 29mm)
- Stock camshafts
- Custom made 2.4mm head gasket to keep compression ratio at 12.5:1
- 60 mm throttle body
- 60 mm MAF
- Stainless steel intake with K&N filter
- Group A chip to take care of ignition
- Apexi Afc Neo to take care of fuel
- Fuel pressure regulator
- Modified fuel rail
- Walbro fuel pump
- Custom made 1.75" 4-1 extractors and 2" exhaust
- Lightened and balanced flywheel 9.5lb
- Samurai pressure plate
- 3 puck clutch disc
- Straight cut custom made gears (1st 2.8, 2nd 2, 3rd 1.6, 4th 1.2 and fifth gear is the stock one)
- Stock 4.11 diff (for christmas Santa is gonna get an LSD for me)
- Suspension has Custom made lower springs (front 7.5 Kilos and rear 9 kilos) and custom made shocks (stock are 20mm, mine are 24mm and they are "serviciable", you can open the top and refill them to get a harder or softer oil in them any time)
- All the bars are in there, upper and lower, front and back with poly bushings all around
- Stainless steel brake lines all around and CRX calipers on the front and bigger nissan 240 pads in the rear (they are a bolt on cheap upgrade)

Here is a video of it before the new pistons and valves, sorry for the awful driving but I never drag raced before so I got a little heavy footed in the start and got traction around 6 seconds after the launch, by the way the mercedes I was racing against has an AMG engine and has around 300HP but it was no match for a Swift GTi

Here is another one and you can hear the straight cut gear box working ... 195089.htm

I`ll try to get more videos soon with the new meaner engine.

Author:  freak2demon [ Thu Nov 13, 2008 6:16 pm ]
Post subject:  Re: G15A CONVERSION


I manage to get hold of a G15A block too. Just to ask, how high can you rev?


Author:  G15B [ Thu Nov 13, 2008 6:28 pm ]
Post subject:  Re: G15A CONVERSION

I`ve taken it to 8000 without any issues but I don`t really want to push it any further, you already have it built or you are in the process?
Feel free to ask anything any time.

Author:  freak2demon [ Thu Nov 13, 2008 6:42 pm ]
Post subject:  Re: G15A CONVERSION

thanks for your fast reply. I'm in the process of building it. This are the stuffs I have:

- G15A block
- 75mm 11:1 pistons
- G13B Dohc head ported & polished with oversized SS valves
- Racing Valves Springs & titanium retainers
- Group A camshafts
- 1mm Metal Gasket
- 60 mm throttle body
- 50 mm MAF
- Sard Fuel pressure regulator
- MK1 Fuel rail
- Walbro fuel pump
- Genie Header
- ACT clutch
- 4.4 FD with Suzukisports LSD
- ACL bearings
- Crankscraper

Btw for the gearbox, which gearbox are you using? G13 or G15?
How much of power are you getting?


Author:  G15B [ Thu Nov 13, 2008 7:29 pm ]
Post subject:  Re: G15A CONVERSION

I`m using both because the front half is from the G15 to fit the block because if you use the g13 bell housing you will have to weld into the housing to align the bolts and I dont feel comfortable weldind an aluminium housing, if you use the g15 housing you will also need to use the g15 flywheel because the starter seats a lot higher in the g15 housing and it won be able to catch the g13 flywheel because it as a lot smaller in diameter than the g15 one, I also recomend you to get the g15 right half axle shaft because the bolt pattern to the block is different between the g15 and g13, you will also need to fabricate a piece to get the engine mount into place, there are other things to take into account, you will need to use the g13 water pump, 125 teeth honda b20 timing belt and the g13 tensioner and other little things you will have to look at later.
You can take my expirience because it took me alost to weeks to get it all sorted out but now I have done 2 and its like a walk in the park, by the way now that i remember, you will have to modify your header because the head is now sitting more than 1" higher and you wont have clearance between the carter and the header, you will have to get the secondary tubes enlarged to fit.

The engine is with just 100 Km old but as soon as I get 1k I will take it to the dyno but I guess it should be around 155-160 bhp.

What pistons are you using, g13 oversized? take into account that the compression height of the g13 pistons is 29,1 and the g15 ones is 28,4 and you might have troubles with it.

Author:  freak2demon [ Thu Nov 13, 2008 7:55 pm ]
Post subject:  Re: G15A CONVERSION

thanks alot for your information. it really helps in building my g15. Looks like I have lot of fabrication to do. I'm using 75mm pistons. They are g15/g16 pistons. They are not oversized.

Author:  G15B [ Thu Nov 13, 2008 10:33 pm ]
Post subject:  Re: G15A CONVERSION

Where did you got those pistons? I`ve been looking for g15/16 high compresion pistons but never found them so I had to use the P29 and get a really tall head gasket to compensate for the taller pistons

Author:  freak2demon [ Fri Nov 14, 2008 12:15 pm ]
Post subject:  Re: G15A CONVERSION

I bought them fm a friend. At first, I couldn't find one so thought of using PM7 or P29 pistons. Somehow manage to find one. lucky me.

Author:  G15B [ Sat Nov 15, 2008 9:28 am ]
Post subject:  Re: G15A CONVERSION

Lucky you

Author:  4 banger [ Sat Nov 15, 2008 11:56 am ]
Post subject:  Re: G15A CONVERSION


Author:  mzeeshan [ Sat Nov 29, 2008 12:49 pm ]
Post subject:  Re: G15A CONVERSION

well dudes there are thousands of pistons available for g15 and g16 both

Author:  master40 [ Sun Jun 07, 2009 2:50 pm ]
Post subject:  Re: G15A CONVERSION

bro i hav done the same swap in my gti but unfortunately i lost the power which i have before car is too fast before head swap on my g15a n i was doing around 137 to 140 at 400 my question is this tht after this swap the cmpression looses to 8.5 smthing as told my what you think that due to low compression it is not running good or any thing else??????
and another thing that im using same ECU as well as wirring n all sensors of g15 including im not pro in modification so i want to know that if i'll change my distributor with g13b one will there will be any change or using around 1.2mm headgaskit!!!!!!!!!

Author:  4 banger [ Wed Jun 10, 2009 9:34 am ]
Post subject:  Re: G15A CONVERSION

yes compression is your problem here...u'll need to replace the pistons to higher compression ones...stock 75mm pistons on the G15 block with the G13B head is a no no....

Author:  weaponR [ Wed Jun 10, 2009 11:13 am ]
Post subject:  Re: G15A CONVERSION

what type of maf are you using that is 60mm?

Author:  G15B [ Wed Jun 24, 2009 8:43 pm ]
Post subject:  Re: G15A CONVERSION

Ford 4.0 Maf, but it needs an Apexi to control fuel, mine is set at -21 so you can figure how much air get through there.

About that power loss, the G15 combustion chamber is 5cc smaller to compensate for the dished pistons, so your compression is really low now and compression = power, I didn`t undestand what ECU you are using but the G15 ECU is made for economy and driveability, not performance so the fuel and ignition curves are not optimized for the GTi head wich also has different camshafts, you have to use the heads ECU, not the blocks one, also use the GTi sensors.

Author:  VR4 [ Thu Jun 25, 2009 11:25 am ]
Post subject:  Re: G15A CONVERSION

pulling that much airflow signal to get your AFRs correct will = insane amounts of timing advance.

Author:  claude b [ Thu Dec 31, 2009 7:06 pm ]
Post subject:  Re: G15A CONVERSION

its good to have company wt ppl using the g15a engine, im also going thru the paces and doing a total restoration along with a performance upgrade.
i was told the g15a engine cannot be revved beyond 6500 continuously and be reliable, my intention is to make 250+whp and dip my feet in some weekend racing. this is the progress ive made so far, i try to keep it as detailed as possible that any1 interested can get factual info. is it ok i ask a couple questions to clarify many of the things im not clear about? ... c=117880.0

Author:  claude b [ Thu Dec 31, 2009 7:15 pm ]
Post subject:  Re: G15A CONVERSION

i was told the rods are the major weak point, that i need to get stronger/custom rods made to handle the power. the recommendation was to find one of those rods and piston manufacturing co like ARP, send one of mine and have them custom make the internals. i was told to get longer rods and pistons wt the gudgeon pins higher that the CR is still kept low for boosting but the rod length ratio would be better, any word on that?

i plan on using the greddy emanage ultimate or the MS3 for tuning, utilizing all posible features like flat shifting, launch controller, antilag and even a water/meth tank onboard for when i flip 2 high boost. tuning for ignition and fuel, this im intending to learn.

Author:  stephennmm [ Fri Jan 01, 2010 3:53 am ]
Post subject:  Re: G15A CONVERSION

Hey, did you have to modify anything for the honda valves other then the normally for the larger valves??? And what valve springs are you using??? And so you know for a pressure plate honda k20/k24 pressure plate bolts onto the 1.6 sidekick flywheel. Dont know if that helps with the d15 because i havent really heard much on that motor. Thanks Stephen

Author:  turbohull [ Wed Jan 13, 2010 12:25 pm ]
Post subject:  Re: G15A CONVERSION

nice find on the pressure plate :thumb2: that's good to know

Author:  rozzzzz [ Thu Mar 18, 2010 10:48 am ]
Post subject:  Re: G15A CONVERSION

my mk1 with g15a..done few days back

41572.jpeg [ 65.26 KIB | Viewed 9761 times ]
49489.jpeg [ 58.21 KIB | Viewed 9764 times ]

Author:  claude b [ Sun Mar 28, 2010 12:49 am ]
Post subject:  Re: G15A CONVERSION

@ rozzzzz.
nice man, u got anymore pics?

@ stephennmm
wonderful find in deed, will see if i can do some investigating on what other flywheel bolts to the g15a.

Author:  instant_shine [ Tue Jul 30, 2013 2:53 pm ]
Post subject:  Re: G15A CONVERSION

How about timing belt?

Author:  koko [ Wed May 13, 2015 3:56 am ]
Post subject:  Re: G15A CONVERSION

Hi experts,

I have got a G15a installed in my old Margalla and i have to say that the engine is ridiculously fast. It spins the wheels even on the second gear :D . What more i can do to increase the horse power. Your suggestions are much appreciated. Thank you.

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