I agree Dusty. You and I did Exactly that with Fear. We had to losen up the converter about 400rpms to take some of the snap off the 10.5 tires. Let the boost do the rest
Forced Induction's FI91X report!
- Thread starter Alky V6
- Start date
The decision was made to go with a divided turbine housing. The same basic a/r, 1.15. The thinking being that the divider wall actually takes up volume in the scroll that's not adjusted for with larger diameters through the scroll. In essence, actually creating a smaller area in the a/r ratio that puts the computed ratio below 1.0. The new turbine housing will also hug the turbine wheel all the way to the inducer diameter which should also help. This will mean that shaft plays will have to be periodically checked carefully to prevent the turbine wheel inducer from crashing into the turbine housing in the case of excessive shaft endplay. I'll post some comparison pics when the new housing shows up.
Tony Shoaff
Active Member
- Joined
- Apr 24, 2006
DAM DONNIE,
I like time you have spent both testing and posting.Awesome! I am racing Sunday and will time the spool and psi. I will let you know.
I like time you have spent both testing and posting.Awesome! I am racing Sunday and will time the spool and psi. I will let you know.
With the scroll of the split turbine housing obviously being a tighter design, radius wise, but the a/r labelling being identical (1.15), that can only mean that the scroll internal area is less.
To maintain a particular a/r ratio, if you go down on the number of either the area or the radius, you must also go down on the other to maintain the ratio. The smaller radius and area dimensions can only cause an increase in exhaust flow velocity.
On the split housing, the extra material inside the scroll, above the point where the major diameter tip closest to the radius leading to the minor diameter, is aiming the exhaust gases more towards the base of the turbine wheel, causing the exhaust gases to stay in contact with the turbine wheel longer and more (all) of the gases actually working on the major diameter. The way the open turbine housing was machined, a good portion of the exhaust gases was allowed to bypass the major diameter and exit the turbine wheel with less work transferred to the turbine wheel.
It will be interesting to see how effective the new split housing is, as far as decreasing spool time.
To maintain a particular a/r ratio, if you go down on the number of either the area or the radius, you must also go down on the other to maintain the ratio. The smaller radius and area dimensions can only cause an increase in exhaust flow velocity.
On the split housing, the extra material inside the scroll, above the point where the major diameter tip closest to the radius leading to the minor diameter, is aiming the exhaust gases more towards the base of the turbine wheel, causing the exhaust gases to stay in contact with the turbine wheel longer and more (all) of the gases actually working on the major diameter. The way the open turbine housing was machined, a good portion of the exhaust gases was allowed to bypass the major diameter and exit the turbine wheel with less work transferred to the turbine wheel.
It will be interesting to see how effective the new split housing is, as far as decreasing spool time.
In the pictures of the views pointing straight into the turbine entrance, you can see how the separate passages of the split housing squeeze, or funnel the exhaust gases into a tighter stream to feed the turbine wheel, increasing exhaust flow velocity.
Got things back together. I left the compressor inlet piping off so I could watch the compressor wheel and it does look promising. The comp wheel is spinning at a faster, more respectable speed at idle and it reacts quicker and spins up faster when I blip the throttle out of gear.
With my small displacement and tight torque converter, spooling this monster is definitely challenging. Probably would go much better if I wasn’t so stubborn and went with a higher stall T/C. I just changed the stator in the T/C and the stall is now 2730 rpm (up 300 rpm) with an a/f ratio of .78 lambda (5.03:1). I found that the mixture had to be within 1 percent to achieve the highest stall speed out of the T/C. O2 correction is off. This is the stall speed without the nitrous assist. I’m tuning in the fuel map without the nitrous first. With the nitrous, it should add around 1,000 rpm to the stall. I’ve found, so far, that to maintain the steepest boost rise, the mixture is very critical. My fuel map is close, but not perfect. Still dialing it in. When a too-lean or too-rich spot on the map is hit during the boost rise, you can see the map rise reading slow until the mixture becomes optimum again. When I get the mixture consistent throughout the boost rise, it should be quicker and smoother.
The top end a/f ratio is coming in nicely also. I’m using .73 lambda (4.7:1) after the turbo is well spooled and the thing is amazing. At first with the new turbo, with the boost controller set at 24 psi and the wastegate cranked in tight, I would be able to reach 24 and it would control well. Now, with the mixture more optimum on the top end, the boost controller still set at 24 psi, the boost is spiking to 312 kPa and settling at 300 kPa for the rest of the run. I'll need to take some preload off of the wastegate now. The fuel pump booster is cranked all the way to 50% and the mixture looks safe (4.7:1) for 300 kPa.
Things are looking promising. I haven’t hit any walls yet that would appear to be limiting me yet (except traction issues
). After the fuel map is set, then there’s still the nitrous to tune in, the T/C stall to play with, torque converter feed control to try. One way or another I’ll make this work.
On one of the 300 kPa runs, after hitting 3rd gear, the car proceeded to do a burnout through the whole 3rd gear with me having to throttle the baby across the finish line. I'll be doing single passes until I have this car dialed in better. I'm thinking of putting a down force wing over the back of the car. I wonder how much they really work.
The top end a/f ratio is coming in nicely also. I’m using .73 lambda (4.7:1) after the turbo is well spooled and the thing is amazing. At first with the new turbo, with the boost controller set at 24 psi and the wastegate cranked in tight, I would be able to reach 24 and it would control well. Now, with the mixture more optimum on the top end, the boost controller still set at 24 psi, the boost is spiking to 312 kPa and settling at 300 kPa for the rest of the run. I'll need to take some preload off of the wastegate now. The fuel pump booster is cranked all the way to 50% and the mixture looks safe (4.7:1) for 300 kPa.
Things are looking promising. I haven’t hit any walls yet that would appear to be limiting me yet (except traction issues
). After the fuel map is set, then there’s still the nitrous to tune in, the T/C stall to play with, torque converter feed control to try. One way or another I’ll make this work.On one of the 300 kPa runs, after hitting 3rd gear, the car proceeded to do a burnout through the whole 3rd gear with me having to throttle the baby across the finish line. I'll be doing single passes until I have this car dialed in better. I'm thinking of putting a down force wing over the back of the car. I wonder how much they really work.
I retarded the ignition timing 2 degrees to 32 and the new stall figure is 2,795 rpm with the map reading bouncing between 96.5 and 98.5 kPa. Atmospheric pressure with my system is 98 kPa. Being able to reach 98 kPa at stall is a major accomplishment. With the last turbine housing, I didn't see 98 kPa until between 4,500 to 5,200 rpm during my roll out.
Latest in the adventures of spooling a 91mm turbo with a 224cid Buick V6.
The nitrous shot is now 245. Mixture is perfect. Timing while on nitrous is still being worked out.
The spool up rate is as follows:
144kPa by 5650 rpm
203 kPa by 6744 rpm
Not bad at all. Way too much boost for the 1-2 shift with these tires.
AMS-1000 is being installed.
Enough data has been collected that I was able to put together a table of future jetting of the nitrous system if higher hp settings are needed, all the way up to a 345hp shot. I seriously doubt a 345 shot will be needed, judging by the progress that's been made by going from a 200 to a 245 shot.
The car is down for improvements. One will be to build a cylinder bank separating wall in the exhaust collector Y-pipe and up to the wastegate valve to take full advantage of the split pulse turbine housing.
The nitrous shot is now 245. Mixture is perfect. Timing while on nitrous is still being worked out.
The spool up rate is as follows:
144kPa by 5650 rpm
203 kPa by 6744 rpm
Not bad at all. Way too much boost for the 1-2 shift with these tires.
AMS-1000 is being installed.
Enough data has been collected that I was able to put together a table of future jetting of the nitrous system if higher hp settings are needed, all the way up to a 345hp shot. I seriously doubt a 345 shot will be needed, judging by the progress that's been made by going from a 200 to a 245 shot.
The car is down for improvements. One will be to build a cylinder bank separating wall in the exhaust collector Y-pipe and up to the wastegate valve to take full advantage of the split pulse turbine housing.
Good info! Faster spool and more boost
OK, that is some good stuff. I'm going to hold off dividing the Y-pipe for now, just in case I want to modify my adapter flange later.
The idea is to take the limited volume of exhaust flow and squeeze it into a smaller passage to increase pressure and velocity at the turbine wheel. Like closing your thumb on the end of the garden hose to increase the pressure and velocity of the water exiting the hose. The focused energy turns the turbine wheel quicker.
Still, I have a simpler solution since I already have THE system in place. Instead of modifying how the limited exhaust flow is plumbed to the turbine wheel, why not just increase the amount of exhaust flow. Like opening the valve to the water hose or increasing the supply pressure to the garden hose, leaving the end of the hose wide open so that back pressure doesn't creap into the picture.
And just how would you increase the exhaust volume off boost on a turbocharged engine?
Very simple.
MORE NITROUS PLEASE!!!
The idea is to take the limited volume of exhaust flow and squeeze it into a smaller passage to increase pressure and velocity at the turbine wheel. Like closing your thumb on the end of the garden hose to increase the pressure and velocity of the water exiting the hose. The focused energy turns the turbine wheel quicker.
Still, I have a simpler solution since I already have THE system in place. Instead of modifying how the limited exhaust flow is plumbed to the turbine wheel, why not just increase the amount of exhaust flow. Like opening the valve to the water hose or increasing the supply pressure to the garden hose, leaving the end of the hose wide open so that back pressure doesn't creap into the picture.
And just how would you increase the exhaust volume off boost on a turbocharged engine?
Very simple.
MORE NITROUS PLEASE!!!
It's hard to say. It's definitely more than the T76 ever produced at any boost setting.
The lowest boost I've had the 91 at has been 24 psi so far. I need to change the wastegate spring package to get the boost lower. Even at 24 I couldn't get the tires to stick enough to get a good ET and mph. It's funny having to work the boost down to get a better pass. I'm going to be working on getting those fresh 29x10.5-15w tires on during this down time (notching frame), and the better boost controller.
One other mod is going to be a camera mount for inside the car so that I can record some readings, like exhaust back pressure.
The best run so far in the 1/8th with the 91 has been a 6.7x at 113.x with a 1.66 60 foot. That is with me pedaling through just about all of 2nd gear trying to get traction, finally short shifting to 3rd. The 60 foot will get fixed with more tuning of the nitrous system. We'll see if the new tires will be up to the task. Depending on how the nitrous system improves the 60 foot, I may be going back to 3.73 gears too.
I have heard the cars get tough to work with when they are light. Maybe look into some suspension issues while doing the tire swap. I think you should be able to hook a non W tire no problem. Second gear has always been a forget about it gear for me, but 3rd can be tricky when the track is a little bumpy and not prepped well.
The tight converter is not going to be very forgiving if you don't bring the power on easy also. The AMS-1000 will give you almost infinite resolution over this. I have heard of some really nailing the tune up recently with the Innovative Boost controller also so if you have one of them that is also a option.
The tight converter is not going to be very forgiving if you don't bring the power on easy also. The AMS-1000 will give you almost infinite resolution over this. I have heard of some really nailing the tune up recently with the Innovative Boost controller also so if you have one of them that is also a option.
The car is just over 3,000 lbs with me in it, so it's not a super light weight. I agree with you there. I have no plans of making the car lighter. If anything, adding weight over the rear. Larger fuel cell, Intercooler water tank.
I presently am using the Innovative controller. An AMS-1000 is on the desk sitting in the wings. I think the AMS will be easier to get the control I'm looking for. I know that just the addition of a CO2 bottle would help out the Innovative controller too, but the AMS has more bells and whistles to play with.
A TRZ roll bar is going on the car also as part of the upgrade list.
I'm going to hang onto the tight T/C as long as I can. The only trouble I see it causing at this point is the boost spike I get during the 1-2 shift (drop in rpm of 800 to 1,200 depending on the shift rpm point) causing a loss of traction. The spike being caused by the boost controller not being able to react with enough authority. No CO2 and the boost climbing at a steep rate just before and during the shift with the rpm dropping so much. The CO2 alone will do wonders for that. Snap that valve way open.
I get what you mean about 2nd gear. So you need to run a lower target boost through all of 2nd? Or, do you ramp it up slowly?
I presently am using the Innovative controller. An AMS-1000 is on the desk sitting in the wings. I think the AMS will be easier to get the control I'm looking for. I know that just the addition of a CO2 bottle would help out the Innovative controller too, but the AMS has more bells and whistles to play with.
A TRZ roll bar is going on the car also as part of the upgrade list.
I'm going to hang onto the tight T/C as long as I can. The only trouble I see it causing at this point is the boost spike I get during the 1-2 shift (drop in rpm of 800 to 1,200 depending on the shift rpm point) causing a loss of traction. The spike being caused by the boost controller not being able to react with enough authority. No CO2 and the boost climbing at a steep rate just before and during the shift with the rpm dropping so much. The CO2 alone will do wonders for that. Snap that valve way open.
I get what you mean about 2nd gear. So you need to run a lower target boost through all of 2nd? Or, do you ramp it up slowly?