[Santos]

Installed bigger jets on my sierra today.
The jets where available in 2.5 increments. So i increased the primary from stock 99 to 102.5 and the secondary from 105 to 115.

2.5 years ago i put 141 in the secondary before a trip to stockton beach (based on the fact i pulled them from a g13A swift) The car climbed the hills on the newcastle/sydney freeway like a rocket with 3 people doing 100kms on inclines i usually keep 90km solo. I took them out though as it was commented that a small cloud of black smoke came out everytime i hit the accelerator. Interestingly i didn't have that much difference in fuel consumption despite them being 34% bigger. Since then i have been looking for something around the 120 mark

anyway finally found some mikuni jets that work . 115 was the largest i could get from an australian supplier and at 9.5% richer than stock it will be interesting how it fairs on the trip to stockton this weekend.

As for the 102.5 i decided to get them instead of the 100 option as 3.5% richer didn't seem like a big increment particularly when i run 95RON E10 frequently. Verdict, idles way to high even when winding the idle jet in. Took it for a spin around the block and it pulls nicely with 0 throttle up a small incline. So i going to pull it out and put the 99 back in and just ordered 100. I'll save the 102.5 for the 1397cc motor i'm building this year.

Took some photos and i'll do a full write up including the brass float and other pieces i did when i get back from stockton. Just thought i'd start a thread now to see if there is interest.

[303zuke]

There is interest. Continue

[droverdave]

Got any other engine mods? cam/exhaust/compression?

Be interesting to get a wideband going.

[Zook_Fan]

I had one of the sierra's I owned tuned as part of a carby rebuild. The car had extractors, 2 inch exhaust, single muffler and cat with no other known engine mods. The primary went up to a 102.5 and the secondary was around 122.5. It pulled very hard for a 1.3, fuel economy didn't seem any different from any other stock sierra I drove around.

[sideways]

303zuke wrote:

There is interest. Continue

X2

[Santos]

Put the 99 back in but she still idles higher than normal 1200 rpm cold, 1500rpm hot
102.5 jet was 1500 cold 2000rpm hot so its an improvement. Was 1000 to 1200 yesterday.
Hot idle is turned completely off

i suspect either
-a vacuum leak somewhere
- need to increase float level
-

100 jet is probably going to arrive tommorow so i sort it out then, i need to save my energy for a drive out to blacktown and back from northern beaches

Pity the damn idle jet screw is so awkward to get to. I think i may just mount the carb backwards, tune it and then put it right way round

The car is stock. Stock tyres, gearing, engine, exhaust ect. The only changes are a rebuilt modded aisin carb and modded stock intake both done under design cues comparing various vitara and swift G motor intakes

Don't have access to a wideband and its out of my budget for now.

Once i sort out the little gremlins (and test it out to, from and on stockton) i'll add the photos etc

[JrZook]

Cool stuff!

Just a note:

If you increase the jet diameter by x% the fuel flow is actually increased by x^2% as the flow is directly proportional to the cross-sectional area of the jet and therefore proportional to the diameter squared. So for example your jetting increase of 34% in diameter actually results in ~180% fuel flow increase!

[BlueSuzy]

I had a few swift carbs and found the larger jets out of them then put into the sierra's. Went mad, Fumes killed me, so did k's per tank


Then went Efi.

[Santos]

JrZook wrote:

Cool stuff!

Just a note:

If you increase the jet diameter by x% the fuel flow is actually increased by x^2% as the flow is directly proportional to the cross-sectional area of the jet and therefore proportional to the diameter squared. So for example your jetting increase of 34% in diameter actually results in ~180% fuel flow increase!

thats a good point... never thought of that! Hopefully the 100 jet will be a sucess then.


Anyway the trip to woodcroft and back was sucessful. Traffic sucked which means i could pay attention to what appeared to ba a hunting idle. Then i noted that when i was on the downhill it sat at 1000-1100 and when i was on uphills it was closer to 1450. So i'm thinking its most likely the new brass float. Will adjust it by the book tomorrow.

[Santos]

Just an update, went to stockton with 99/115 jets
Didn't have a chance touch it but the idle seems to have settled this week at 1000rpm so i think maybe the new brass float had to bed in or something.

Currently mulling over putting the 102.5 back in for another go or swaping in the 100.

[Aaron]

i have a 1.3 carb that i got rebuilt, im not sure what size the jets are but the guy who did it knew what to increase them by. i have high compression pistons, 272 torquer cam, extractors, 2 inch exhaust and mine seems to fly compared to my brothers stock 1.3

[Santos]

Aaron wrote:

i have a 1.3 carb that i got rebuilt, im not sure what size the jets are but the guy who did it knew what to increase them by. i have high compression pistons, 272 torquer cam, extractors, 2 inch exhaust and mine seems to fly compared to my brothers stock 1.3

open it and look

[zedboy]

Sounds good, where can you buy the jets? Also how much are they approximately?

[Santos]

Welcome zedboy. Mikuni Main jets $5 each + post.

http://www.ebay.com.au/itm/NEW-MIKUNI-C ... 4cfd73201e

Be sure not to get hexhead ones. i got them initially thinking they would be more robust but they dont fit. (most old jets i have pulled damaged screwdriver slots)

Currently running 102.5/115. It idles normally now, when i had 99/115 i actually had a slight improvement in kilometerage. Gained aprox 500 to 600m a litre. Results with the 102.5 appears promising, going to give it a few more tanks. Having done several trips to newcastle and back, 102.5 have definattely been an improvement in sub 80kms speads. i think i still need to go slightly bigger on secondaries, ZookFan's configuration might be the magic number after all.

[zedboy]

Thanks for that Santos

I think I'll try the 102.5/122.5 combo. Are they easy enough to change? I am mechanically minded and have 2 nissans which I have built both making over 320kw @ the wheels though I've never touched carbys haha. My dad's the old school mechanic so I might get him to do it.

I'm currently run 31x10.5 MTZ, 2" spring and 2" body lift, and low range 6.5's in the trasfer case. If this mod gives me a bit more power without killing fuel consumption that would be awesome currently getting around 11.5/100km.

Matt.

Santos wrote:

Welcome zedboy. Mikuni Main jets $5 each + post.

http://www.ebay.com.au/itm/NEW-MIKUNI-C ... 4cfd73201e

Be sure not to get hexhead ones. i got them initially thinking they would be more robust but they dont fit. (most old jets i have pulled damaged screwdriver slots)

Currently running 102.5/115. It idles normally now, when i had 99/115 i actually had a slight improvement in kilometerage. Gained aprox 500 to 600m a litre. Results with the 102.5 appears promising, going to give it a few more tanks. Having done several trips to newcastle and back, 102.5 have definattely been an improvement in sub 80kms speads. i think i still need to go slightly bigger on secondaries, ZookFan's configuration might be the magic number after all.

[Santos]

zedboy wrote:

Thanks for that Santos

I think I'll try the 102.5/122.5 combo. Are they easy enough to change? I am mechanically minded and have 2 nissans which I have built both making over 320kw @ the wheels though I've never touched carbys haha. My dad's the old school mechanic so I might get him to do it.

I'm currently run 31x10.5 MTZ, 2" spring and 2" body lift, and low range 6.5's in the trasfer case. If this mod gives me a bit more power without killing fuel consumption that would be awesome currently getting around 11.5/100km.

Matt.

Keeep in mind I run stock tyres, stock gearing, zero body lift and my OME leafs have probably lost their 40mm gain. It keeps it zippy enough for me, have yet to go anywhere that i find myself wishing i had bigger tyre/gearing/lift. Ultimately i'm sure there is a 16v g16b in your future if you want to keep the car, its the way most go its a proven set up.

If you are going straight to 122.2 may i suggest you get this 4 pack of 120,125,130,135 instead? you can start with 125 and shift up or down based on your driving test. I did run 141 originally and it was strong (fuel in this case dropped a bit but barely) . Just hated the thought of the little black dumps everytime i shifted gear/touched the accelerator.

Changing the jets is fairly easy, just download the sierra manual. Its 5 philip head bolts, 4x 12mm and 2x 14mm on the float bowl. Just remember where the auto-choke & polution gear went, be aware of not tipping the cab upside down to pull it apart (little springs and ball berrings shoot out) My recommendation is lay an old sheet or tarp under the car to catch anything you drop. Lastly be aware of the float, they can be a little brittle with age which is why i now have 80's toyota landcruiser brass floats(destroyed a few on several suzuki carbs, i think the foam dries out)

[303zuke]

Santos wrote:

Changing the jets is fairly easy, just download the sierra manual.

I beleive most, if not all the downloadable manuals feature the World market Hitachi carb, while Aust market Sierras use an AISIN carb. So far, the only manual I have found for these is a hard copy factory original supplement. Have you found a download with the AISIN supplement?

[Santos]

303zuke wrote:

Santos wrote:

Changing the jets is fairly easy, just download the sierra manual.

I beleive most, if not all the downloadable manuals feature the World market Hitachi carb, while Aust market Sierras use an AISIN carb. So far, the only manual I have found for these is a hard copy factory original supplement. Have you found a download with the AISIN supplement?

actually no, i have personally always used the hardcopy

but suzukiinfo.com has a 72mb file that says scaneed locally. I'm certain its an aussie host.

[Santos]

Just an update, the car engine had appeared to be slowly dying over the 6 months. First i couldn't get it to rev past 3500rpm or go faster than 70km/hr or 30kms up hills. Compression test, vacuum test and idle where all fairly god so i ws a little stumped. Turned out my accelerator cable had seized and i was not getting a response when driving (but would when i was standing ovr the engine bay operating throttle by hand) Given that i had y sisters excel and a friends vitara to drive/work-on i left the car parked. At the worst top speed was 40kms on fat and wuldn't do hills without momentum.

Anyway snapped a accelerator pedal driving it again, once that happened the mystery revealed itself, replaced pedal and cable and everything is rocking along and pulls nicely. Primary jets are 100 and secondary still 115

I'm bringing this up as i have a 1397cc motor that is getting a rebuilt carb and i'm thinking of starting the jetting at 102.5/105 for primary and ordered 127.5 for the secondary.

[sideways]

Might be of interest to some..

I'm rebuilding a 4K Corolla carb at the moment, they're basically the same as the 1.3l Aisin carb but with less vacuum gear, a manual choke and 2mm larger throats. It's so similar that I'm using a Sierra carby kit in it.

It's got a 108 primary and 153 secondary. It was pulled off a dead stock KE70.

Also, I pulled a 142 out of a TB42 Patrol carb that fits perfectly, though it has a slightly longer thread. If I remember correctlly, JDK81 was running 108 & 142 in a Sierra carb on a G16a with good results.

303zuke wrote:

Santos wrote:

Changing the jets is fairly easy, just download the sierra manual.

I beleive most, if not all the downloadable manuals feature the World market Hitachi carb, while Aust market Sierras use an AISIN carb. So far, the only manual I have found for these is a hard copy factory original supplement. Have you found a download with the AISIN supplement?

For those after this, the Holden Drover manual you can download it here.

http://www.suzukiinfo.com/sierra/

It's interesting to note that the Drover manual also shows a manual choke variation.

[Santos]

sideways wrote:

Might be of interest to some..

I'm rebuilding a 4K Corolla carb at the moment, they're basically the same as the 1.3l Aisin carb but with less vacuum gear, a manual choke and 2mm larger throats. It's so similar that I'm using a Sierra carby kit in it.

It's got a 108 primary and 153 secondary. It was pulled off a dead stock KE70.

Also, I pulled a 142 out of a TB42 Patrol carb that fits perfectly, though it has a slightly longer thread. If I remember correctlly, JDK81 was running 108 & 142 in a Sierra carb on a G16a with good results.

I have pulled a 141 jet out of a 1st generation 'boxy' 1.3l suzuki swift. The carb was the same a sierra one just a few different bolt on bits (throttle cable bracket etc) Figured seeing it came out of a g13a engine i'd be sweet. Drove it up to stockton with 3 people in the car and was so happy that it was holding 110-115 in areas i have struggled to 105 without any passengers. The other sierra a weber equip LWB had trouble keeping up (he had one passenger on 30's i had 27's) Would of left them in if my mate the passenger in the other car hadn't of said that a small puff of black smoke popped out every time i did a sudden hit the accelerator

I find in sydney winters the 102.5 smells a little rich. Keep us posted on the 108's. I'm starting to think genuine mikuni jets are a must as they are supposed to have a 5-10% flow variation (eg a 100 could be 90-110!) but generic brands aren't necessary equivalents (egbrand 'x' 100 does not necessarily = mikuni 100 and has its own flow variation)

sideways wrote:

303zuke wrote:

Santos wrote:

Changing the jets is fairly easy, just download the sierra manual.

I beleive most, if not all the downloadable manuals feature the World market Hitachi carb, while Aust market Sierras use an AISIN carb. So far, the only manual I have found for these is a hard copy factory original supplement. Have you found a download with the AISIN supplement?

For those after this, the Holden Drover manual you can download it here.

http://www.suzukiinfo.com/sierra/

It's interesting to note that the Drover manual also shows a manual choke variation.

The standard (non-USA) SJ413 manual also shows a manual choke variation. The later SJ80 Coily factory manuals (says Sj413 on cover for 97-98) also have a manual choke from memory along with Fuel injection (TBI)


I happen to now have my hands one of these manual choke carburetors.