Nevada_TDI
Top Post Dawg
So, get some sandpaper and sand the ridges off of the housing while making an attempt to keep it "round", or is that not an option?
Turbo stop screw adjustment
- Thread starter martinlink
- Start date
martinlink
Well-known member
I would think the bore in the housing(s) is already too large so the air can escape without building boost. Sanding would only make it worse if that is the case...
Nevada_TDI
Top Post Dawg
I am talking about sanding the manifold where it goes into the down pipe. All of the velocity used to spool the turbo is upstream of the "exit". If lowering the pressure or velocity was a bad idea, there would never be a down pipe larger than the one that comes stock with the engine, right? The greater the pressure drop after the vanes, the greater amount of exhaust can be moved through to allow more boost to be generated, theoretically helping to lower EMP.
martinlink
Well-known member
But the issue is with the turbo housing itself, where the impellers have hit the wall and made the bore wider. This causes the exhaust gases to flow past the blades without spinning them, I would think, so sanding anything downstream the turbo would not have a positive effect 
Bear in mind the car is stock, and what I am currently trying to achieve is stock performance before I start modding anything. So I'd like to find and fix the initial reason for the bad performance without bypassing it with other mods
Bear in mind the car is stock, and what I am currently trying to achieve is stock performance before I start modding anything. So I'd like to find and fix the initial reason for the bad performance without bypassing it with other mods
martinlink
Well-known member
Alright! So I finally got a matching turbo with perfect housings and put my CHRA into it. Straight off the bat, it's miles better than the previous setup ever was!
In 3rd, it takes 2 seconds to make full boost - this took 7 seconds previously.
Here's a graph in 3rd from ~1500rpm:
Sorry for it not being up to 4k, I just moved and there aren't many long stretches of road up here...
I'm achieving full boost at about 2100rpm which is still a little too high for a small turbo like this. Also note the duty factor (light blue thin line) is high, so I know the actuator rod needs shortening by 2 threads maybe.
Could it be enough to shorten the actuator rod to get the boost down to 1700rpm, or will I need to mess with the stop screw, too?
If needed, I have some more logs in both 3rd and 4th.
Thanks!
In 3rd, it takes 2 seconds to make full boost - this took 7 seconds previously.
Here's a graph in 3rd from ~1500rpm:
Sorry for it not being up to 4k, I just moved and there aren't many long stretches of road up here...
I'm achieving full boost at about 2100rpm which is still a little too high for a small turbo like this. Also note the duty factor (light blue thin line) is high, so I know the actuator rod needs shortening by 2 threads maybe.
Could it be enough to shorten the actuator rod to get the boost down to 1700rpm, or will I need to mess with the stop screw, too?
If needed, I have some more logs in both 3rd and 4th.
Thanks!
Nevada_TDI
Top Post Dawg
You mention your car is stock, it isn't tuned to start making boost that low.
With the new CHRA did you check the actuator movement; at how much vacuum did it start moving, and at how much vacuum did it hit the stop screw?
Your car is stock, please set actuator travel to factory setting and then move on from there. You need a solid baseline to start from.=
With the new CHRA did you check the actuator movement; at how much vacuum did it start moving, and at how much vacuum did it hit the stop screw?
Your car is stock, please set actuator travel to factory setting and then move on from there. You need a solid baseline to start from.=
martinlink
Well-known member
I set the actuator up to start moving at ~5inHg and it touched the stop screw at 19inHg. But the thing is, I can't be sure the stop screw is set right as I copied the length from the CHRA the new housing came with, and I probably couldn't get it ideal.
At what rpm does a stock 1.9 with the gt1749v make full boost? I'd like to at least achieve that before I start messing with it further.
Also, it's not 100% stock now that I think of it, the cats are emptied and also EGR is deleted.
At what rpm does a stock 1.9 with the gt1749v make full boost? I'd like to at least achieve that before I start messing with it further.
Also, it's not 100% stock now that I think of it, the cats are emptied and also EGR is deleted.
Nevada_TDI
Top Post Dawg
You are going to have to pull the actuator out of the way to do this>>>
Here is the optimum setup if you can get it to happen: 1) back the set screw down a couple of turns or so, 2) pull the actuator towards the screw stop and it will hit the internal ring stop spot, 3) gently turn stop screw in until screw touches arm lever, 4) turn stop screw in 1/2 turn and lock it into place, 5) now set the lift and stop points of the actuator: 3-3-1/2" vacuum when arm starts to move and 18" of vacuum when it hits the stop screw. This will get you very close to factory turbo action on the stock tune you now have. If at some point you install a tune in your car, the turbo start and stop points will stay where they are, and is why you need to go "back to the factory" setup of your turbo. It is very likely when you put in your tune your turbo will not act correctly UNLESS your turbo is set back to "stock" settings.
I know from experience... I did not set my actuator correctly in the stock tune and when my tune was upgraded it was all spikes and over boost until I reset the turbo.
Here is the optimum setup if you can get it to happen: 1) back the set screw down a couple of turns or so, 2) pull the actuator towards the screw stop and it will hit the internal ring stop spot, 3) gently turn stop screw in until screw touches arm lever, 4) turn stop screw in 1/2 turn and lock it into place, 5) now set the lift and stop points of the actuator: 3-3-1/2" vacuum when arm starts to move and 18" of vacuum when it hits the stop screw. This will get you very close to factory turbo action on the stock tune you now have. If at some point you install a tune in your car, the turbo start and stop points will stay where they are, and is why you need to go "back to the factory" setup of your turbo. It is very likely when you put in your tune your turbo will not act correctly UNLESS your turbo is set back to "stock" settings.
I know from experience... I did not set my actuator correctly in the stock tune and when my tune was upgraded it was all spikes and over boost until I reset the turbo.
martinlink
Well-known member
Alright, so you're confirming that 1/2 turn off the mechanical stop is the correct place for the screw. I noticed that the CHRA I used to set mine was about 1 full turn off the mechanical stop - maybe it was set up wrong as well... Might have been refurbed at some point even though the housings were pristine.
Yesterday I shortened the actuator rod by 1.5 turns just to see what results I get - I can do it with the turbo still on the car. As suspected, spool speed was not affected at all and I started getting spikes of 2.65bar with the requested at 2.4bar. They were compensated for by the n75 as duty factor decreased to 30%, but they lasted a bit too long for my liking (over 1 second). I think I'll reset it and leave the fine tuning to when the stop screw is where it should be.
By the way, would winding the stop screw outwards induce a spike when actual meets requested? On the graph the curve is quite flat, slowly meeting requested.
Also worth mentioning, I emulated the 1400rpm test (like block 11 in vagcom) by keeping the rpm at 1400 and toggling vacuum on/off. The difference was 130mbar which should be in the right range...? What am I aiming for when it's just right?
So the next step is to find a garage where I can adjust the stop screw outwards by 1/2 turn and we'll go from there.
Thanks for the input so far, we're almost there
Yesterday I shortened the actuator rod by 1.5 turns just to see what results I get - I can do it with the turbo still on the car. As suspected, spool speed was not affected at all and I started getting spikes of 2.65bar with the requested at 2.4bar. They were compensated for by the n75 as duty factor decreased to 30%, but they lasted a bit too long for my liking (over 1 second). I think I'll reset it and leave the fine tuning to when the stop screw is where it should be.
By the way, would winding the stop screw outwards induce a spike when actual meets requested? On the graph the curve is quite flat, slowly meeting requested.
Also worth mentioning, I emulated the 1400rpm test (like block 11 in vagcom) by keeping the rpm at 1400 and toggling vacuum on/off. The difference was 130mbar which should be in the right range...? What am I aiming for when it's just right?
So the next step is to find a garage where I can adjust the stop screw outwards by 1/2 turn and we'll go from there.
Thanks for the input so far, we're almost there
martinlink
Well-known member
Had some time on my hands today (sadly no access to a garage to adjust the stop screw) so I decided to dial in the actuator length. Logged various settings and made a few graphs to make it easier to pick the "winner":
Rod with 8 threads showing, spike at 2540mbar, N75 duty at 36%:
Rod with 7 threads showing, spike at 2650mbar, N75 duty at 31%:
I'm not getting ~20% on the N75 duty (as most guides suggest) and I'm afraid to shorten the rod below 7 threads showing since the spike could be about 2750mbar then
Original setting in the previous posts was 9.5 threads showing, it was a bit lazy there so I'd think between 9 and 8 is the sweet spot where it spikes up to 2500mbar max. Seeing as it will be mapped after it's dialed in, I wouldn't want too big of a spike as it will probably be even higher after the map...
Rod with 8 threads showing, spike at 2540mbar, N75 duty at 36%:
Rod with 7 threads showing, spike at 2650mbar, N75 duty at 31%:
I'm not getting ~20% on the N75 duty (as most guides suggest) and I'm afraid to shorten the rod below 7 threads showing since the spike could be about 2750mbar then
Original setting in the previous posts was 9.5 threads showing, it was a bit lazy there so I'd think between 9 and 8 is the sweet spot where it spikes up to 2500mbar max. Seeing as it will be mapped after it's dialed in, I wouldn't want too big of a spike as it will probably be even higher after the map...
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Nevada_TDI
Top Post Dawg
I have already read the below post, but I want to answer your question. One-half turn is not perfect in all situations, but neither is one-full turn either. What I mean is all of our vnt's due to age and machining tolerances etc., are not going to be set at the exact same place. The point is when the actuator requests boost you don't want the vanes to potentially crash shut into each other and stick that way causing potential serious damage to anything under the hood.Alright, so you're confirming that 1/2 turn off the mechanical stop is the correct place for the screw. I noticed that the CHRA I used to set mine was about 1 full turn off the mechanical stop - maybe it was set up wrong as well... Might have been refurbed at some point even though the housings were pristine.
Yesterday I shortened the actuator rod by 1.5 turns just to see what results I get - I can do it with the turbo still on the car. As suspected, spool speed was not affected at all and I started getting spikes of 2.65bar with the requested at 2.4bar. They were compensated for by the n75 as duty factor decreased to 30%, but they lasted a bit too long for my liking (over 1 second). I think I'll reset it and leave the fine tuning to when the stop screw is where it should be.
By the way, would winding the stop screw outwards induce a spike when actual meets requested? On the graph the curve is quite flat, slowly meeting requested.
Also worth mentioning, I emulated the 1400rpm test (like block 11 in vagcom) by keeping the rpm at 1400 and toggling vacuum on/off. The difference was 130mbar which should be in the right range...? What am I aiming for when it's just right?
So the next step is to find a garage where I can adjust the stop screw outwards by 1/2 turn and we'll go from there.
Thanks for the input so far, we're almost there
Nevada_TDI
Top Post Dawg
Personally, I wouldn't want a spike over 2400mbar on a regular basis. 2275mbar is the safe "long term" limit for the 1749v turbo aka 18-PSI for those of us not in Europe. How is a non-tuned 1749v running more than 1900mbar anyway? Your signature shows an MB not a VW, oops.Had some time on my hands today (sadly no access to a garage to adjust the stop screw) so I decided to dial in the actuator length. Logged various settings and made a few graphs to make it easier to pick the "winner":
Rod with 8 threads showing, spike at 2540mbar, N75 duty at 36%:
Rod with 7 threads showing, spike at 2650mbar, N75 duty at 31%:
I'm not getting ~20% on the N75 duty (as most guides suggest) and I'm afraid to shorten the rod below 7 threads showing since the spike could be about 2750mbar then
Original setting in the previous posts was 9.5 threads showing, it was a bit lazy there so I'd think between 9 and 8 is the sweet spot where it spikes up to 2500mbar max. Seeing as it will be mapped after it's dialed in, I wouldn't want too big of a spike as it will probably be even higher after the map...
martinlink
Well-known member
Yeah, it's a BMW e46 320d, the requested boost is about 2350mbar when the car is stock...
The vanes on this turbo are quite far apart so even in the most shut position they don't really touch.
I plan on running the car at 1400rpm and unscrewing by 1/4 turns - I'm aiming for 180mbar difference between idle and 1400rpm. Currently at 140mbar or so.
The vanes on this turbo are quite far apart so even in the most shut position they don't really touch.
I plan on running the car at 1400rpm and unscrewing by 1/4 turns - I'm aiming for 180mbar difference between idle and 1400rpm. Currently at 140mbar or so.
martinlink
Well-known member
Well, that plan failed - there's just not enough space down there to efficiently judge the amount of turns I do on the screw, let alone tighten it in a controlled fashion...
Currently it's at a position where the difference is around 160mbar but the spool speed hasn't changed, I still hit full boost at roughly 2100rpm. I can't find any definite answers as to when a properly set up one should hit full boost, but the standard for a gt1749v should be around 1800rpm.
I have loads of logs with the actuator length set at various settings, here's one with the actuator at 9 turns showing, difference between idle and 1400rpm at 160mbar, 3rd gear:
And here's one with a custom remap, other parameters the same (don't worry about the overboost, it has already been corrected!):
So, any ideas on what to try next? File down the stop screw from above, one micrometer at a time?
Thanks for the input so far!
Currently it's at a position where the difference is around 160mbar but the spool speed hasn't changed, I still hit full boost at roughly 2100rpm. I can't find any definite answers as to when a properly set up one should hit full boost, but the standard for a gt1749v should be around 1800rpm.
I have loads of logs with the actuator length set at various settings, here's one with the actuator at 9 turns showing, difference between idle and 1400rpm at 160mbar, 3rd gear:
And here's one with a custom remap, other parameters the same (don't worry about the overboost, it has already been corrected!):
So, any ideas on what to try next? File down the stop screw from above, one micrometer at a time?
Thanks for the input so far!
Nevada_TDI
Top Post Dawg
I must be missing something, the hex key tools I have all have a 90 degree bend on the end making the ability to count "turns" easy like the hands on a clock.
martinlink
Well-known member
On this car I'm doing it from the underside and in a way that renders me blind while I do the adjustments (the screw is right above one of the engine mounts). I can roughly turn it by feel, but when trying to lock the screw down with the nut, I have no idea if the screw turns along with it or not
Also, doing all of this with the engine still warm from driving to the garage makes all of it very imprecise... Without a similar car's logs I'm pretty much just guestimating and trying to find the best setting, meanwhile not knowing where it should ideally be.
Also, doing all of this with the engine still warm from driving to the garage makes all of it very imprecise... Without a similar car's logs I'm pretty much just guestimating and trying to find the best setting, meanwhile not knowing where it should ideally be.
poisas
Veteran Member
you can make it spool faster via making more turbo lag... also max spool depends on stopscrew being to high. if you lower it to certain position in can start to spool later, but turbo adjustments has to be made after remap...