Wastegate port size?

hensleyt

Well-Known Member
Joined
Feb 20, 2008
My 5857 port size is out to .970.Think it was around .800 when I started. I just cant get it under control. (It better)
Spike is the worst from the dig on the street if the tires spin, if I roll into it,the turbo smart street can keep it under 20. (was shooting for 17 on the street)I'm OK with that. If I get a little to heavy footed it spikes to 30 and my Alky cant stop the KR.
At the track it has been OK ,I have my track boost set for 26,and see a1lb spike at the 2-3 shift.Sometime it will carry through at 27,and sometimes it will come back down to 26.
How BIG can I go in size or should I be looking somewhere else?
I don't see any red under lines sorry for my spelling,but it dose not effect my ability to read a set of dial caliper or understand there is a lot that can case boost spike besides the port size.
Thank you for your time
 
I have a GN1 3.5 Downpipe . I ported my turbine housing and waste gate hole so they match up as well as I could get . This turbo is a CompTurbo CT43 7168 Triple ball bearing . It is a bad ass turbo that spools lighting quick . #CompTurbo
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You should disconnect the waste gate flap and see if you can build boost . If you can’t that is a good thing because then you would know your waste gate hole will be able to flow freely and it would point you towards your boost controller settings. If it builds boost with it disconnected then you have some porting in your future . Some more porting pics
 

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With the small turbo you will get some boost drop off with RPM unless you have closed loop boost control and you are in a controllable range of boost. If you are using a manual controller, not surprised that you are getting a spike. The spike probably gets higher if you peak the boost at a lower RPM. I get a little boost drop off with the 5858. I use closed loop boost control which dampens out the spikes and helps with the drop off. A better boost controller would probably eliminate all of the drop off and spikes so long as the turbo is not at max capable boost throughout the RPM range. My waste gate hole is the standard PTE .63 housing size.
 
Thanks Chuck & Dank
I’m 99% sure I’m plumed right and the over boost is set correct in my street setting , I’ll go back through it again , it’s been awhile.
I have read removing the actuator Over and over and I don’t remember to try that befor I removed the turbo
With the turbo off do you think 1 in is overkill
Thanks
 
hensleyt,

My set up is using an internal gated 3" THDP with 1.5" puck .
I understand if you go to an external waste gate set up that matching the waste gate hole to your DP is needed.

Conversely,with an internal WG if you go too large on the hole u to control over boosting / spike, you may run into problems running at higher boost levels achieving those boost levels, as the pressure from the larger hole and the resulting forces pushing your puck off the opening as much more spring pressure is required.

I needed to open up my waste gate hole on the precision .63 A/R exhaust housing from Precisions' 0.90" opening to 1.10" and radius the underside edge in order to control boost spike and boost creep. Just running 94 octane gas, no Alky.

I am in the process of installing a Garrett .63 A/R exhaust housing on my turbo and this has a 0.82" opening. (Trying to compensate for too low a stall on my converter).
Told my machinist to open it up to 0.95" and radiusing the underside edge and will begin trial testing in the spring time.
I'm leaning on purchasing and installing Razor's Alky kit and don't want to open the hole up too much, but want to be able to control the spike which occurs very quickly on my DBB 5857SP .

Good Luck , keep us posted on your progress.
 
Instead of trying to compensate for your torque converter you should just install the right one with the right stall for your application. I have been using west coast converters / Edge racing converters for awhile now and have had great luck with them . I would get something like a 9” 3200 stall lock up . You can get one from them for like $550-600 .
 
Instead of trying to compensate for your torque converter you should just install the right one with the right stall for your application. I have been using west coast converters / Edge racing converters for awhile now and have had great luck with them . I would get something like a 9” 3200 stall lock up . You can get one from them for like $550-600 .


dank GN,
Thanks for your suggestions.
A far less expensive approach would be to send my 9X11 Torque converter back to TCS in Arizona for a re-stall. At around $200 it's the cheapest option.
Since I live in Canada, Buying new gets pretty expensive very quickly, due to the currency exchange rate of +30% and an additional +13% HST (Harmonized Sales Tax) we are forced to pay at the border. So, that $550-$600 Torque Convertor is gonna actually cost $807-$881 at the end of the day it's much less $ to install the .63 A/R Garrett Exhaust Housing that I've got sitting on the shelf. Besides there's much less labour in the housing install vs dropping the transmission to install a new torque convertor.
 
hensleyt,

My set up is using an internal gated 3" THDP with 1.5" puck .
I understand if you go to an external waste gate set up that matching the waste gate hole to your DP is needed.

Conversely,with an internal WG if you go too large on the hole u to control over boosting / spike, you may run into problems running at higher boost levels achieving those boost levels, as the pressure from the larger hole and the resulting forces pushing your puck off the opening as much more spring pressure is required.

I needed to open up my waste gate hole on the precision .63 A/R exhaust housing from Precisions' 0.90" opening to 1.10" and radius the underside edge in order to control boost spike and boost creep. Just running 94 octane gas, no Alky.

I am in the process of installing a Garrett .63 A/R exhaust housing on my turbo and this has a 0.82" opening. (Trying to compensate for too low a stall on my converter).
Told my machinist to open it up to 0.95" and radiusing the underside edge and will begin trial testing in the spring time.
I'm leaning on purchasing and installing Razor's Alky kit and don't want to open the hole up too much, but want to be able to control the spike which occurs very quickly on my DBB 5857SP .

Good Luck , keep us posted on your progress.

This is where tuning comes into play. Here's what you do. Take that Gen 2 and throw it in the nearest large body of water...Lake Ontario will do. Grab 2 chips from Eric. A 94 street chip with 20 lbs of fuel in it. The other a 112 race chip...piss on alky. Dial up the low gear timing and drag down the low gear 02's. It'll spool like a mad whore with the Precision housing on it. You TO guys make things tough on yourselves. It's so easy...it's scary. Left you my cell number.:):cool:
 
I was uncertain from the original post that you have an electronic boost controller, I am unfamiliar with the turbosmart boost controllers. What kind of initial boost settings does it have? Make sure that the waste actuator is at the minimum tension that allows the max boost that you want. Also, the initial waste gate duty cycle should be set to stop the spike then let the boost controller ramp the waste gate setting assuming it is closed loop or has other features to do this. The lower the RPM, the more prone to a boost spike, that is why you see a bigger spike on the street then when at the track and you are WOT through the whole run from a standstill.
 
Turbosmart is a open loop like OEM.and has lots of features to help spool and help over boost.(meaning it can be a little complicated)I will get the Turbo back on tomorrow,and go over the settings before I drive it.double check the pluming.I may have something wrong,I was 99% sure it was working ok and it just need a bigger port.Im on the fence right know.
I’ll be be trying it after I have checked all settings buy running it with the actuator off and actuator wired at max open stroke.
Actuator started moving at 8-10 psi and full stroke just under 30,no leaks good and smooth.
I may have had this problem for a while,the SCM-G logs at 2.0 TPS and 1.1 KR and has only been on the car for a year.
 
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