Yep...I'm 0 for 3.
06-10-2008, 11:16 PM
#21
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Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
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Originally Posted by 89t295k' post='901303' date='Jun 1 2008, 06:56 PM
You have two possible causes IMO:
1. detonation witch will not happen at 11 afr unless your timing is way off for the bridgeport. Verify the pully to the stock one, timing lock and unlock. U can run well with very retarded timing next time to eliminate that.
2. Missfire from being too rich, bad cas, or more likely RFI as Lynn said. I had oil on my wires once and it missfire like mad, put new wire on and it got ten times better, moved them to different position and it went away.
Week later I got one missfire at 3rd gear wot 18psi, then several more the next time b4 I cracked back dowl landing. Don't know 4 sure if it was a progressive problem then finally went or one real bad hit...btw I was at 10.5-11afr as I have run for 2 +years and thousands of boosts.
I am rebuilding it right now and found my cas to have a pretty wide gap compaired to others I have looked at-I'm hoping that is or was part of the ignition problem being so sensitive. It also doesn't help that I have a FC1000 amp too. Sometimes I would see a jump on the datalogs.
I have been told to make sure the engine will rev perfectly b4 boosting as it is a decent test for irradic firing. Data log it too for being smooth.
Also those housing look like the holes ar in different locations lol.
Was the engine fully warm when you did it in the morning?
I feel your pain. Focus on the ignition and give it another try.
Scott
1. detonation witch will not happen at 11 afr unless your timing is way off for the bridgeport. Verify the pully to the stock one, timing lock and unlock. U can run well with very retarded timing next time to eliminate that.
2. Missfire from being too rich, bad cas, or more likely RFI as Lynn said. I had oil on my wires once and it missfire like mad, put new wire on and it got ten times better, moved them to different position and it went away.
Week later I got one missfire at 3rd gear wot 18psi, then several more the next time b4 I cracked back dowl landing. Don't know 4 sure if it was a progressive problem then finally went or one real bad hit...btw I was at 10.5-11afr as I have run for 2 +years and thousands of boosts.
I am rebuilding it right now and found my cas to have a pretty wide gap compaired to others I have looked at-I'm hoping that is or was part of the ignition problem being so sensitive. It also doesn't help that I have a FC1000 amp too. Sometimes I would see a jump on the datalogs.
I have been told to make sure the engine will rev perfectly b4 boosting as it is a decent test for irradic firing. Data log it too for being smooth.
Also those housing look like the holes ar in different locations lol.
Was the engine fully warm when you did it in the morning?
I feel your pain. Focus on the ignition and give it another try.
Scott
Here is a tidbit to think about.
There are some things that remain the same no matter what else is going on inside an engine. The flame speed of a mixture is just about the same for any given pressure, no matter the RPM.
The engine timing is adjusted to produce the ideal torque (highest cylinder pressure) at about 50 degrees ATDC. Higher boost=higher effective compression=faster flame speed. So, with the boost up, the advance required to get the highest cylinder pressure at 50 degrees, needs to be retarded to account for the higher flame speed.
So you might see much more advance at partial throttle, coasting and light throttle cruise situations. Light throttle and closed throttle gives you way less than the rated compression ratio, because the inlet is being restricted, and the cylinder cannot fill completly. So, 10:1 might become 7:1 or 8:1 compression, That is where the advance comes back up. Very little fuel to light, and poor compression to help sustain the flame. So, the big timing head start gets the fire going early and that brings up the cylinder pressure for a bit more heat and a more complete fuel burn.
So when off the power, there is no concern for the proper angle for torque, since you are not calling for power, the concern is for a good burn and lowered polution levels (HC).
So the engine controller must be able to sweep the timing from less than zero (ATDC) to 35 degrees (BTDC) in near zero time.
The compression ratio is then variable based on the amount of boost. Let us say that you determine that the effective compression ratio at 6,000 RPM and 30 pounds of boost is 13.7:1. How much advance is required now?
The timing is measured at the crank just like the piston engine. So one can imagine that 35 degrees on a piston engine has some relationship with 35 degrees on a rotary. It does not. The rotor is moving like molasses and the crank is turning three times faster than the rotor. That 35 degrees on a rotary is only 11.6 degrees at the rotor. The rotor also spends a lot of time at or near the TDC position (Dwell). There is plenty of time to burn all of the fuel available. A piston engine spends very little time at or near TDC (Dwell) and needs lots of advance to get anything burned.
So, gobs of advance is not required on a rotary. On an NA engine 20 (6.6 degrees at the rotor), total is plenty up to 9,000 RPM. In a boosted engine far less.
In engines with no electronic timing management, it is possible to detonate the engine at very low speed, by just opening the throttle wide. Suppose you are in thrd gear just barely moving along, you need to accelerate but instead of dropping down to 2nd you just bury the throttle pedal. The cylinder filling suddenly goes to 100% or slightly more. The timing is whatever it should be for the dismal speed you are going, say 15 degrees BTDC. The engine is turning only 1,200 RPM.
The car shudders as you crack a corner seal. ???????
The timing for fast idle is far more advanced than is required for full throttle 100% cylinder filling. The flame speed for full throttle (full cylinder) burn with highest pressure at 50 degrees ATDC is 3 degrees ATDC. The lack of vacuum will now retard the timing about 1/2 revolution after that seal cracks. The effect here is that since the rotor will not move by the TDC position before all of the fuel has burned, the cylinder temperature will go too high, and the upper apex seal will be the location for the start of a second flame front.
The moral here is slow down on the full throttle move. Give the loss of vacuum a chance to work. Drop down to the the proper gear before accelerating. The engine will respond properly and all of the pieces will remaine in tact.
Lynn E. Hanover
06-11-2008, 06:00 AM
#22
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Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
Posts: 1,322
Originally Posted by Lynn E. Hanover' post='901780' date='Jun 10 2008, 08:16 PM
Here is a tidbit to think about.
There are some things that remain the same no matter what else is going on inside an engine. The flame speed of a mixture is just about the same for any given pressure, no matter the RPM.
The engine timing is adjusted to produce the ideal torque (highest cylinder pressure) at about 50 degrees ATDC. Higher boost=higher effective compression=faster flame speed. So, with the boost up, the advance required to get the highest cylinder pressure at 50 degrees, needs to be retarded to account for the higher flame speed.
So you might see much more advance at partial throttle, coasting and light throttle cruise situations. Light throttle and closed throttle gives you way less than the rated compression ratio, because the inlet is being restricted, and the cylinder cannot fill completly. So, 10:1 might become 7:1 or 8:1 compression, That is where the advance comes back up. Very little fuel to light, and poor compression to help sustain the flame. So, the big timing head start gets the fire going early and that brings up the cylinder pressure for a bit more heat and a more complete fuel burn.
So when off the power, there is no concern for the proper angle for torque, since you are not calling for power, the concern is for a good burn and lowered polution levels (HC).
So the engine controller must be able to sweep the timing from less than zero (ATDC) to 35 degrees (BTDC) in near zero time.
The compression ratio is then variable based on the amount of boost. Let us say that you determine that the effective compression ratio at 6,000 RPM and 30 pounds of boost is 13.7:1. How much advance is required now?
The timing is measured at the crank just like the piston engine. So one can imagine that 35 degrees on a piston engine has some relationship with 35 degrees on a rotary. It does not. The rotor is moving like molasses and the crank is turning three times faster than the rotor. That 35 degrees on a rotary is only 11.6 degrees at the rotor. The rotor also spends a lot of time at or near the TDC position (Dwell). There is plenty of time to burn all of the fuel available. A piston engine spends very little time at or near TDC (Dwell) and needs lots of advance to get anything burned.
So, gobs of advance is not required on a rotary. On an NA engine 20 (6.6 degrees at the rotor), total is plenty up to 9,000 RPM. In a boosted engine far less.
In engines with no electronic timing management, it is possible to detonate the engine at very low speed, by just opening the throttle wide. Suppose you are in thrd gear just barely moving along, you need to accelerate but instead of dropping down to 2nd you just bury the throttle pedal. The cylinder filling suddenly goes to 100% or slightly more. The timing is whatever it should be for the dismal speed you are going, say 15 degrees BTDC. The engine is turning only 1,200 RPM.
The car shudders as you crack a corner seal. ???????
The timing for fast idle is far more advanced than is required for full throttle 100% cylinder filling. The flame speed for full throttle (full cylinder) burn with highest pressure at 50 degrees ATDC is 3 degrees ATDC. The lack of vacuum will now retard the timing about 1/2 revolution after that seal cracks. The effect here is that since the rotor will not move by the TDC position before all of the fuel has burned, the cylinder temperature will go too high, and the upper apex seal will be the location for the start of a second flame front.
The moral here is slow down on the full throttle move. Give the loss of vacuum a chance to work. Drop down to the the proper gear before accelerating. The engine will respond properly and all of the pieces will remaine in tact.
Lynn E. Hanover
There are some things that remain the same no matter what else is going on inside an engine. The flame speed of a mixture is just about the same for any given pressure, no matter the RPM.
The engine timing is adjusted to produce the ideal torque (highest cylinder pressure) at about 50 degrees ATDC. Higher boost=higher effective compression=faster flame speed. So, with the boost up, the advance required to get the highest cylinder pressure at 50 degrees, needs to be retarded to account for the higher flame speed.
So you might see much more advance at partial throttle, coasting and light throttle cruise situations. Light throttle and closed throttle gives you way less than the rated compression ratio, because the inlet is being restricted, and the cylinder cannot fill completly. So, 10:1 might become 7:1 or 8:1 compression, That is where the advance comes back up. Very little fuel to light, and poor compression to help sustain the flame. So, the big timing head start gets the fire going early and that brings up the cylinder pressure for a bit more heat and a more complete fuel burn.
So when off the power, there is no concern for the proper angle for torque, since you are not calling for power, the concern is for a good burn and lowered polution levels (HC).
So the engine controller must be able to sweep the timing from less than zero (ATDC) to 35 degrees (BTDC) in near zero time.
The compression ratio is then variable based on the amount of boost. Let us say that you determine that the effective compression ratio at 6,000 RPM and 30 pounds of boost is 13.7:1. How much advance is required now?
The timing is measured at the crank just like the piston engine. So one can imagine that 35 degrees on a piston engine has some relationship with 35 degrees on a rotary. It does not. The rotor is moving like molasses and the crank is turning three times faster than the rotor. That 35 degrees on a rotary is only 11.6 degrees at the rotor. The rotor also spends a lot of time at or near the TDC position (Dwell). There is plenty of time to burn all of the fuel available. A piston engine spends very little time at or near TDC (Dwell) and needs lots of advance to get anything burned.
So, gobs of advance is not required on a rotary. On an NA engine 20 (6.6 degrees at the rotor), total is plenty up to 9,000 RPM. In a boosted engine far less.
In engines with no electronic timing management, it is possible to detonate the engine at very low speed, by just opening the throttle wide. Suppose you are in thrd gear just barely moving along, you need to accelerate but instead of dropping down to 2nd you just bury the throttle pedal. The cylinder filling suddenly goes to 100% or slightly more. The timing is whatever it should be for the dismal speed you are going, say 15 degrees BTDC. The engine is turning only 1,200 RPM.
The car shudders as you crack a corner seal. ???????
The timing for fast idle is far more advanced than is required for full throttle 100% cylinder filling. The flame speed for full throttle (full cylinder) burn with highest pressure at 50 degrees ATDC is 3 degrees ATDC. The lack of vacuum will now retard the timing about 1/2 revolution after that seal cracks. The effect here is that since the rotor will not move by the TDC position before all of the fuel has burned, the cylinder temperature will go too high, and the upper apex seal will be the location for the start of a second flame front.
The moral here is slow down on the full throttle move. Give the loss of vacuum a chance to work. Drop down to the the proper gear before accelerating. The engine will respond properly and all of the pieces will remaine in tact.
Lynn E. Hanover
I note that in one picture of your fantastic installation, that it looks like intake air is being collected from inside the engine compartment. Detonation is charge temperature dependant. Intake air must be the lowest temperature air available. At the top of the radiator opening or the center of the cowl.
Lynn E. Hanover
06-12-2008, 11:30 AM
#23
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Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by Lynn E. Hanover' post='901780' date='Jun 10 2008, 09:16 PM
The moral here is slow down on the full throttle move. Give the loss of vacuum a chance to work. Drop down to the the proper gear before accelerating. The engine will respond properly and all of the pieces will remain intact.
Lynn E. Hanover
Lynn E. Hanover
one of the neat things about obd2/whatever they call it now, is that you can take a new rx8, and the mazda diagnostic computer (its nothing fancy, same software as we had at hyundai) and go drive around and either watch or datalog the timings vs throttle position.
what you find is that mazda runs very steep curves, 2500rpm in 6th, and its running 40degrees advance, hit the gas, and it'll drop to almost tdc at the same rpm. give it half throttle, and about 3/4 of the advance goes away... the curves it runs are WAY steeper and taller than we're used to putting in our aftermarket ecu's....
the rx8 (prolly due to emissions) doesnt get to its peak wot timing (30L with a split, between 8-12 it varies a little) until 6000rpms, from 2500 and about tdc its a long slow climb....
06-15-2008, 12:00 PM
#24
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Originally Posted by j9fd3s' post='899403' date='Apr 27 2008, 01:22 AM
so i just built a motor, and checked tdc, and the "factory" marks were WAY off, like 30+ degrees. it looks like an untouched factory pulley assembly, but all the e shafts are the same, so it cant be.
2, if you're flattening springs its detonating....
2, if you're flattening springs its detonating....
C.Ludwig and I spent some time yesterday to pull the motor and tear it down. Everything looked fine inside, so no issues there. No flattened seals or springs, just a cracked front iron dowel land.
Ludwig rigged up a jig to check TDC using my E-shaft and pulleys. We did discover that the TDC timing mark on my Mazda Racing Pulley was a bit off. We were actually hoping that it would have been off on the advance side to give us some sort of indication that the pulley might have been the cause all along. Instead of being advanced, it ended up being off to the retarded side, 3.5 degrees to be exact.
At this point, after the tear down, the cause is still unknown but there are a couple theories in place. 1) The combination of the pulley timing marks being a few degrees off, along with the the play or "slop" in the CAS, magnifies the possibility that the ECU could see a crazy event leading to firing the plugs at the wrong time, stuttering the motor, shifting the plates, cracking the dowel land.
2) In discussing some of the wiring of the ECU, Coils, and remotely located battery, it might be a possibility that I need to re-wire some grounds in the car. I'll go into more detail on how I have it currently wired to get everyone's thoughts on this theory.
06-15-2008, 12:06 PM
#25
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Originally Posted by Lynn E. Hanover' post='900392' date='May 14 2008, 07:15 PM
I have little skill with boosted engines, and it is a shame to see such a huge amount of work go up in smoke. I have been able to break out a front dowel hole in a 12A NA engine, and there are few people around who can say that. I notice that you have an AN fitting in the vertical gallery adjacent to the dowel hole. Is this a boss and "O" ring fitting, or, a tapered pipe fitting?
The tapered pipe fitting is not used because of the likleyhood of cracking out the hole from stress developed when the fitting is tightened.
In my experience it takes more than a little bit of detonation to break out a dowel hole. However, just one or two preignition events will do it every time at full throttle. I would look for the lead (low voltage) wires to the coils to be separated and run from two locations as far apart as is possible. Could even be run through some dash 4 stainless braid covered hose, with the braid grounded to the chassis. The coil wires should be inductive to help limit RF radiation. The coils should be spaced apart. The high voltage wires should be kept as far apart as possible, and well away from the low voltage wires.
When there is good cylinder filling the amount of energy required to fire a plug goes way up. So one way to prevent a misfire in any kind of system is to gap the plugs real tight. My race plugs are gapped at .010" with dual MSD-6ALs. Never a misfire
up to 9,600 RPM.
You can build a TDC setup like mine and check the timing marks on the pulley and remark them as required, and even better,
bolt on the counterweight and flywheel and add the timing marks to the flywheel teeth, for a super precision timing system.
Make up a cover that has a timing pointer attached.
They do that on aircraft installations for easy timing, standing next to a spinning prop. Done on Cosworth engines as well.
My guess is that you get an occasional induced hit 180 degrees out of sync for that housing.
Another thought. One of the airplane guys uses nitrous to get his amfibious plane out of the water. He shuts off the trailing ignition to prevent detonation during the nitrous. When you think about the definition
of detonation, you could deduce that too much split on the timing could look like detonation to the boosted engine.
On a night after a hot day, the humidity is high, and the oxygen count is low. In the morning after a cool night the dew is the water vapor condensed out of the air, and the oxygen count is high. More power is available in the AM.
Lynn E. Hanover
The tapered pipe fitting is not used because of the likleyhood of cracking out the hole from stress developed when the fitting is tightened.
In my experience it takes more than a little bit of detonation to break out a dowel hole. However, just one or two preignition events will do it every time at full throttle. I would look for the lead (low voltage) wires to the coils to be separated and run from two locations as far apart as is possible. Could even be run through some dash 4 stainless braid covered hose, with the braid grounded to the chassis. The coil wires should be inductive to help limit RF radiation. The coils should be spaced apart. The high voltage wires should be kept as far apart as possible, and well away from the low voltage wires.
When there is good cylinder filling the amount of energy required to fire a plug goes way up. So one way to prevent a misfire in any kind of system is to gap the plugs real tight. My race plugs are gapped at .010" with dual MSD-6ALs. Never a misfire
up to 9,600 RPM.
You can build a TDC setup like mine and check the timing marks on the pulley and remark them as required, and even better,
bolt on the counterweight and flywheel and add the timing marks to the flywheel teeth, for a super precision timing system.
Make up a cover that has a timing pointer attached.
They do that on aircraft installations for easy timing, standing next to a spinning prop. Done on Cosworth engines as well.
My guess is that you get an occasional induced hit 180 degrees out of sync for that housing.
Another thought. One of the airplane guys uses nitrous to get his amfibious plane out of the water. He shuts off the trailing ignition to prevent detonation during the nitrous. When you think about the definition
of detonation, you could deduce that too much split on the timing could look like detonation to the boosted engine.
On a night after a hot day, the humidity is high, and the oxygen count is low. In the morning after a cool night the dew is the water vapor condensed out of the air, and the oxygen count is high. More power is available in the AM.
Lynn E. Hanover
How can I gap plugs that cannot be gapped? The plugs that were in the car at the current time were a fresh set of BUR9EQ's. We were only going to use these plugs up until our pump gas limit of 14psi. I had a set of NGK Racing 10.5's for higher boost levels. I don't even think the 10.5's can be gapped either?
Is there a different plug that I should be running?
06-17-2008, 08:46 AM
#26
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Join Date: Dec 2002
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Please forgive the grade school drawing, but here is an example of how the ground wires are routed throughout the car.
The only (+) power wires that are shown is the 2 gauge wire running from the battery to the (+) post of the remote terminals in the engine bay, and the stock power harness/fuse block wiring which make their connections also on the remote terminals.
Any thoughts/suggestions are welcome.
The only (+) power wires that are shown is the 2 gauge wire running from the battery to the (+) post of the remote terminals in the engine bay, and the stock power harness/fuse block wiring which make their connections also on the remote terminals.
Any thoughts/suggestions are welcome.
06-23-2008, 07:38 AM
#28
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Join Date: Feb 2003
Location: Calgary
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I am gonna lean towards detonaton,to much advance or, some will argue this, but 9's are to hot for what you are doing.. Its not just the boost pressure that picks the plug, its the combustion pressure and heat.. You are at double the rear wheel hp and using a highway plug.. There are other factors which influence this choice, but generally the stock plugs are for stockish setups..In a shop I worked in, we had to install 10.5s through to 11.5's in stock turbo'd cars that went to track events to bring down the knock levels when hot and give the car some safety margin, and thats on stock ecu's on 100 ron gas..
Also when you get on a dyno, you will hit map spots you have never touched on the street,because you are not really driving the car, you part ways with your driving style. I don't gun my car from 3000 in 4th, I usually downshift on the street. Dyno's load cars differently than street driving and every dyno will do it differently.. You may get into shallower or deeper cells than you would on the street.
My dyno has airbrakes which tends to overload on a car with noisey ignitions(rotary), its best to do light pulls first to see where its at.. I am guilty of running cars unmuffled on the dyno, but its not the best way to do it, you cant even hear the start of pinging pull when its unmuffled, and by the time you do , its often to late..
The engine doesnt need to be extra dowelled, pinned or studded for your power levels, its way to easy to go off on tangents with problems and never solve the simplest ones, you end up with a lot of trick parts and a none running car.. Thats the age old problem with the boosted rx7, tuning is such a black art, we tend to buy every trick piece thinking thats gonna be the golden key to taming the motor, when in fact its just the digital numbers that make most of the difference.
Rebuild it again, find a dyno centre that has a knock amp..
Also when you get on a dyno, you will hit map spots you have never touched on the street,because you are not really driving the car, you part ways with your driving style. I don't gun my car from 3000 in 4th, I usually downshift on the street. Dyno's load cars differently than street driving and every dyno will do it differently.. You may get into shallower or deeper cells than you would on the street.
My dyno has airbrakes which tends to overload on a car with noisey ignitions(rotary), its best to do light pulls first to see where its at.. I am guilty of running cars unmuffled on the dyno, but its not the best way to do it, you cant even hear the start of pinging pull when its unmuffled, and by the time you do , its often to late..
The engine doesnt need to be extra dowelled, pinned or studded for your power levels, its way to easy to go off on tangents with problems and never solve the simplest ones, you end up with a lot of trick parts and a none running car.. Thats the age old problem with the boosted rx7, tuning is such a black art, we tend to buy every trick piece thinking thats gonna be the golden key to taming the motor, when in fact its just the digital numbers that make most of the difference.
Rebuild it again, find a dyno centre that has a knock amp..
06-23-2008, 03:20 PM
#29
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Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by Maxt' post='902352' date='Jun 23 2008, 05:38 AM
My dyno has airbrakes which tends to overload on a car with noisey ignitions(rotary), its best to do light pulls first to see where its at.. I am guilty of running cars unmuffled on the dyno, but its not the best way to do it, you cant even hear the start of pinging pull when its unmuffled, and by the time you do , its often to late..
i noticed on the track with my helmet on, was really good for hearing misfires/etc, but yeah hearing knocks/misfires is a problem
do a google search for det cans...
08-04-2008, 02:22 PM
#30
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Well, I'm giving this one more shot.
Here are the plans this time around:
-New OEM front plate (thick dowel land)
-4 New OEM Dowel Pins
-Re-wire Factory Battery Harness (Starter/Alt/Fuse Block)
-Re-wire Ground System using Bus Bar
-Banzai Racing Oil Pan Brace
-Aeromotive Fuel Filter w/ -6 SS lines (replaces factory filter)
-FD Oil Pressure Regulator
-Vacuum/Boost Manifold
-Switch out the factory CAS for a Haltech Hall Effect Sensor w/ Magnets
Also, of course, the rebuild will be done with all NEW OEM O-rings. Everything will be cleaned, inspected, clearanced during the rebuild as well.
C.Ludwig and I will be doing the rebuild and should have this thing back on the road shortly.
Here are the plans this time around:
-New OEM front plate (thick dowel land)
-4 New OEM Dowel Pins
-Re-wire Factory Battery Harness (Starter/Alt/Fuse Block)
-Re-wire Ground System using Bus Bar
-Banzai Racing Oil Pan Brace
-Aeromotive Fuel Filter w/ -6 SS lines (replaces factory filter)
-FD Oil Pressure Regulator
-Vacuum/Boost Manifold
-Switch out the factory CAS for a Haltech Hall Effect Sensor w/ Magnets
Also, of course, the rebuild will be done with all NEW OEM O-rings. Everything will be cleaned, inspected, clearanced during the rebuild as well.
C.Ludwig and I will be doing the rebuild and should have this thing back on the road shortly.