View Full Version : vnt adjustment
TNT!hammond
13-09-2008, 18:55
New poster! (less than 10 posts)
hi can anyone tell me if you wind the grub/bolt in or out to make the boost come in earlier? with thanks
ross
Winding the grub screw out brings it in earlier matey:)
TNT!hammond
13-09-2008, 21:57
New poster! (less than 10 posts)
cheers james.
how much pre load would you say the actuator requires? 5mm of pull or less? or is that a how long is a piece of string type question ? at the minute the boost is fluttering at half throttle and comes in rather late , saying this there is no preload at all on the actuator
cheers for any replies
ross
New poster! (less than 10 posts)
cheers james.
how much pre load would you say the actuator requires? 5mm of pull or less? or is that a how long is a piece of string type question ? at the minute the boost is fluttering at half throttle and comes in rather late , saying this there is no preload at all on the actuator
cheers for any replies
ross
With regards to pre-load see what it does 1st after you adjust the grub screw / allen key head on the grub screw, the grub doesn't take to much adjustment to bring the boost in earlier. When i was playing with mine I managed to get it to boost full 20psi(manifold) @ 1500rpm:eek:
Now got it set to 20psi (manifold)@ 2500rpm which still gives me a hell of a lots of torque steer and getting traction is hard aswell.:D
The actuator works like a normal actuator so tighten it will raise the boost level. If you have the same as me I only managed to get the actuator to hold 1bar and it wouldn't do anymore than that so I had to use a bleed valve to make up the extra i only get a 1 psi spike to 21psi for a sec then settles @ 20psi.
You can now change the turbo type in your profile to VNT :)
Good instructions BTW. i might copy them to articles.
Can you make the text a little larger in the photo?
TNT!hammond
13-09-2008, 23:09
New poster! (less than 10 posts)
cheers Ian :)
And yes i do have a vnt :)
James mine has no grub scre but a bolt inplace . the bolt is wound right out and there is no thread sticking out the other side . It seems as if its set to spool as fast as possible then. Maybe it is the complete lack of pre load on the actuator then? From waht i can see all the grub/bolt does is limit the turnbuckle arm from pulling towards the actuator as much the more thread that sticks out the other side the less over all movement on it . Does that sound right?
thanks again
New poster! (less than 10 posts)
When you unwind the grub screw you must shorten the actuator arm length so that the lever (connecting to the vanes inside) pulls up onto the grub screw stopper position that you set. Dont make it too log lag as you will get spiking. They do run better with higher boost. as above. 20psi + spiking isnt too bad,
I run 15-16 psi and had to make an ext wastegate to stop it spiking and creeping.
Just about to get her on the road. May tweak her boost settings. Hard to get it right as the ext WG opening too early stops the vains opening fully with reduces overval exhaust flow.
TNT!hammond
14-09-2008, 16:16
New poster! (less than 10 posts)
cheers for the info mate:)
TNT!hammond
14-09-2008, 17:41
New poster! (less than 10 posts)
ok , ive got the vnt behaving itself now , comes on nicely and not as harsh and snatchy . I have a 3psi spike which tbf i had on my t25 ( think a electronic controller may be in order?) AFRS are;
idle 14.9
general driving( vac reading) 13.9-15.3 depending on throttle position
wot holds 11.9 @18 psi 4th gear pull hi rpm
are these ok?
Only thing i did notice is as the boostt rises and then suddenly snaps on full the afrs go hi up to 14 for the tiniest amount of time as if boost rises faster then the carb can get fuel in? Is this a common problem and how can i resolve this .
with thanks
ross
You can now change the turbo type in your profile to VNT :)
Good instructions BTW. i might copy them to articles.
Can you make the text a little larger in the photo?
:)
I have uploadad another pic and amended the text:)
New poster! (less than 10 posts)
ok , ive got the vnt behaving itself now , comes on nicely and not as harsh and snatchy . I have a 3psi spike which tbf i had on my t25 ( think a electronic controller may be in order?) AFRS are;
idle 14.9
general driving( vac reading) 13.9-15.3 depending on throttle position
wot holds 11.9 @18 psi 4th gear pull hi rpm
are these ok?
Only thing i did notice is as the boostt rises and then suddenly snaps on full the afrs go hi up to 14 for the tiniest amount of time as if boost rises faster then the carb can get fuel in? Is this a common problem and how can i resolve this .
with thanks
ross
Sounds OK apart from the 14 reading as boost rises,
Whats the spec of your carb matey?
New poster! (less than 10 posts)
as the boostt rises and then suddenly snaps on full the afrs go hi up to 14 for the tiniest amount of time as if boost rises faster then the carb can get fuel in? Is this a common problem and how can i resolve this
It is common and maybe helped by turning the enrichment screw out a bit, say 1/2 a turn. Have another measure, and maybe another adjust.
This allows the enrichment to start a lower boost.
I think I'm right. Could be have to screw it in.
The screw is hidden behind a metal pressed in ball that you need to first drill out. This is located in the end on the enrichment part that's on the side of the carb. I don't have a photo. But could possibly take one if no-one else can supply.
TNT!hammond
14-09-2008, 20:19
New poster! (less than 10 posts)
cheers Ian its a unscrew to release tention on the spring inside i already have the metal drilled out:)
as for spec,
off the top of my head 1m air
125 1st could be a 1mm though
125 2nd
125 main
de chocked and std venturi
does sound under fuelled but this carb seems to do that on another carb i have to run a larger main with the same setup .
i just foundd out that im really under fuelling in fith cruising at 60-70 it says lean (near 16-17)till 7psi.
any ideas i was thinking main and 1st but the main will richen up on boost far too much i think
cheers ross
It is common and maybe helped by turning the enrichment screw out a bit, say 1/2 a turn. Have another measure, and maybe another adjust.
This allows the enrichment to start a lower boost.
I think I'm right. Could be have to screw it in.
The screw is hidden behind a metal pressed in ball that you need to first drill out. This is located in the end on the enrichment part that's on the side of the carb. I don't have a photo. But could possibly take one if no-one else can supply.
This bit
TNT!hammond
14-09-2008, 21:13
yes james , got that all drilled but still no luck
You could try 1.275mm main.
TNT!hammond
14-09-2008, 21:27
;)hahhaha , Ian i had enough trouble finding a 1.25 jet and drills of .05 incriment let alone 0.025 . Also i have the shakes like Amy the crack head Wine house so chances are its already that size or more lol:laugh::agree::D
newbstar*
14-09-2008, 21:36
First post!
glad to see your getting there with setting it up.What boost have you managed to achieve.;)
TNT!hammond
14-09-2008, 21:38
newbstar,
18 psi mate spikes to 21 . Its pretty mad mate:)
How about a 1.3mm then :)
The carbs tend to dribble all the time at idle with that size. But the car feels a lot better than with a 1.2mm. But it feels a lot better with a 1.275 as well. That was an available jet size. I had one.
TNT!hammond
14-09-2008, 22:01
oh sorry Ian i didnt know that , ill try southern carbs tommorow:)
newbstar*
14-09-2008, 22:45
New poster! (less than 10 posts)
do you like the exhaust note on boost.makes the cij sound savage.:smokin:
TNT!hammond
14-09-2008, 23:02
all i can say is its ......... different. got to get used to it tbh a different driving style is required
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