MyT13B

It is my understanding of a blow off valve that it can allow the turbo to spin freely and actually keep its speed up longer since it has less pressure to compress against.

Currently the only place the boost pressure can go is to back feed through the compressor. I can hear this in the air filter and sometimes it blows the base gasket for the plenum.

The cross section area of the blow off valve has about 1/2 the area of the supply tube it is venting when open full. If the pressure in the plenum will drop 15 psi to 1-2 psi almost instantly then I am fairly sure my TPS boost gadget should also let go.

Many of the things you suggest from experience are useful and interesting. I can relate most of it to this project in some way.

Thank you

Gilgamesh

WOW.

This is some old school sorcery.


I remember seeing a couple articles about Jeff Kissel's 2 rotor turbo E mod Sprite a few years ago. looks like there is a good bit of info around about it on racing beat.

This sprite was definitely a high budget build.
Going Solo - Rotary Racer Jeff Kiesel

MyT13B

This is definitely 'Old School' sorcery. I built my first 13B in the early 1980's. This is build #14 for me of which is the 3rd PP engine to play with. The previous intakes were so large that I only had 1/4" of housing left on the sides of the port. These engines ran very nice and were very streetable. I fed them with a pair of rochester one bbl carbs. Needless to say these engines eventually spit out apex seals...... ouch, but these were only test builds.

The Bugeye of Jeff Kiesel is a very expensive car now that is has an ultra high tech motor. I don't even have that much money in my Pickup and race trailer!

DocHoliday89

iTrader: (10)

Have you used copper intake runners with success before? How are attaching them to the housing? Brazing? What about thermal expansion, how does that effect fitment? Why did you choose copper?

MyT13B

Post 11

This is the first time for me to use copper. They seem to be very secure so far. The intake runners slip into the ports easily and I use a rubber compression gasket around the outside to seal the connection. This allows for some movement of the intake due to expansion to keep from prying on the port couplings. I used aircraft permatex as a lube when I installed the port copper as a soft sealant and a lubricant as they were pressed in. I cleaned the excess permatex with alcohol before using the epoxy on the water jacket area. I did not have to sacrifice any tension bolts with the placement of the port either.

MyT13B

I bought a "GReddy clone" for cheap. It came with 2 springs 20# and 10#. I intend to use the 10# spring. The lighter spring allows the valve to open completely at about 15" vacuum and will close around 7" vacuum.. Beware of these cheap units! When I first moved the valve from the seat, it would only move about 1/8". It would bind on the housing on the side away from the outlet hole. I spent a little time porting this area to allow the valve to open smoothly and completely to about 5/8". The 20# spring takes up more room in the chamber and only allows the valve to open about 7/16".

At idle my engine pulls less than 7" of vacuum. So I think this should work well and close when the engine idles or when I ask for more throttle. Waiting for spring to test it though.

MyT13B

The red arrow points to the boost sensing diaphram. The green arrow points to the TPS adder. The blue arrow points to the blow off valve.

In the blow off valve I tried the 10# spring. Gently revving the engine it would open and not allow the boost to build.

I then tried both springs (30#) and the valve would barely open with some boost by closing the throttle. The boost diaphram let go some but not completely.

I then put only the heavy spring (20#) in. It seems to open properly now as well as long enough to let the boost diaphram 'let go'. It looks promising!

MyT13B

I was reading some posts regarding negative split ignition timing for idle and low power situations. I am not sure just how much negative split to use but it is set for about -8 degrees currently. Base timing is TDC for leading, 8 ATDC for trailing. The mechanical advance is set to add 10 degrees.


The blue arrow points to the trailing vacuum advance. It has a new spring which allows 15 degrees of advance at idle (5-7"Hg). The leading vacuum advance only works when the vacuum is more than 7"Hg and can add 7.5 degrees. This improves the vacuum at idle.

peejay

0 leading, 8 ATDC trailing is positive split, not negative split.

MyT13B

If you add in the advance from the vacuum you get 7 BTDC on the trailing and 0 TDC for the leading. This is at idle with 7" vacuum.

When the vacuum gets to 15" then both are equal without adding the mechanical. So maximum total goes to 20 BTDC for both.

Under boost the timing should go to 10 BTDC leading and 3 BTDC trailing with full mechanical advance.

peejay

You're running vacuum advance to the manifold instead of ported vacuum? How well does that even work?

I tried that on my peripheral port years back, and what would happen is the engine would either idle at 1000rpm at next to no vacuum, or it would hang up at 1800-2200rpm because the vacuum cans pulled up a bunch of timing and it was too much timing for the engine to drop down below that point.

With ported vacuum the cans don't get any vacuum with the throttle shut, so the idle is more stable/predictable.

MyT13B

Yes straight manifold vacuum for the cans. on this set up the vacuum reads rather smooth.

On the bridgeport engine I had, the vacuum was very 'bouncy'. So for this one I just set the timing for total of 20 BTDC on each and no vacuum advance. That engine was not boosted so the 20 BTDC max worked well.

MyT13B

Ignition timing update

I connected the leading to a ported vacuum on the throttle body. Base is set at 2 ATDC. With vacuum it can move about +8 degrees. The mechanical can move +12 degrees.

I left the trailing connected to the manifold vacuum. Base is set at 10 ATDC. At idle the vacuum pulls this to 25 BTDC.

The fuel mixture seems to burn better and slightly leaner too. The throttle response from idle is stronger and smoother than using a more 'stock' arrangement.

Revving the engine higher to promote the turbo, I see that the timing from the vacuum is erased (retarded) without hesitation.

The exhaust doesn't seem as nasty in that my eyes don't burn as much! The exhaust is not very hot and there is lots of water too. By comparison the radiator is hot.

Can't wait to drive it

MyT13B

This is a modified rotor for the trailing timing. I removed the top (trailing connectors) since the leading is a wasted spark. I am using the leading path for the trailing spark. The range of timing change was greater than the rotor would allow so I made extension wings from copper to make sure the spark stays on the post in the distributor. The outer face of the copper was trued up on a lathe to keep the clearance uniform.


The factory rotor would start moving away from the post at 20° BTDC. This should stay near the post up to about 35° BTDC.

MyT13B

3 new MSD Blaster2 coils and 1 balast resistor. 2 1980 ignition triggers. One trigger fires 2 coils for the leading timing and the other trigger fires the trailing coil through the resistor. The old coils made a faint blue spark. These coils make a spark that looks like a lightning bolt! The coils are firing NGK RE7C-L spark plugs made for the leading position on the RX8 engine. WOW I have never seen this engine come to life this quickly HOT or COLD.

MyT13B

It has been a while. I got a chance to run the car this last weekend. It seems the 'latching' of the throttle is even more prominent.

I will now add a SPDT micro switch to my TPS throttle boost circuit. This switch will cause the boost portion of the TPS signal to drop when the throttle plate is closed. Even if there is boost against the Boost TPS there will be no 'adder' for boost with the throttle closed. This switch will jump to the boost control once the throttle plate opens around 5° from idle. The boost TPS has some electrical resistance when it is zeroed out. The idle side of the switch will need an equal resistance to this value for a smooth transition when the switch jumps.

MyT13B

Well it has been a long summer of wishing I could race my car. I have been chasing cooling problems and port problems.......

It is common for the stock ports to be fill with a high temp epoxy to run peripheral intake ports. I have had two failures in a row this summer. The ports in the intermediate housing would fracture the epoxy in the ports and lead to stuck side seals or eroded apex seals.

Also the copper tubes began to seep coolant as well.

I decided it was just not necessary to plug the old intake ports. My reason is that 4 and 6 port engines all have the un-used ports capped off but open to the engine. They run fine that way!!! My ports all have a cover where the intake manifold was,..... same difference.

The copper intake tubes presented a challenge to seal. The unique place that I placed them allowed a possible solution. The tension bolt hole that was clear next to the port was the answer. I tapped this hole from both sides with a 1/4 pipe tap as deep as it would reach. This would allow threading in a pipe plug from each side. I inserted one plug and filled the bolt hole with ultra high temp silicone. I then inserted the plug in the other side of the hole. This created a hydraulic pump to push the silicone into the leaks around the copper. The epoxy had been removed or loosened by heat so it was easy to chip that away. The silicone was then put in place of the previous epoxy. During assembly of the engine. the same tension bolt hole was also filled with silicon to make sure no coolant could get into the hole. The new port just barely cut into the bolt passage so it was a good place to pump sealant into.

The bearings in my old ford turbo gave up the ghost. I had a spare set of bearings to use so I set out to fix the turbo. But not to my liking all the bolt going into the exhaust turbine were rusted so bad the they all broke off, boo hoo....

I found a turbo at CX Racing, a GT3570 clone that would fit my exhaust system and forced me to use larger 2" tubing for my compressor side. Previously the intake side was 1-1/2" tube.

So far the engine is not losing coolant (no load) and I hope to test it with the PTO dyno this weekend to make sure it will not over heat or blow coolant into the chambers.

For what it worth .....$5000 so far......

MyT13B

The coolant leaks are fixed it seems. The Holley fuel controller was just not refined enough to consider the range of settings needed for this engine. I could set the fuel pressure to 30 psi and make it run well from mid to high rpm but not for the bottom end. If I set the fuel pressure to 20 psi the engine ran well from idle to about 5500 where it would run out of fuel. I have since purchased a MSP Pro Ultimate system. I have this set up for a fuel only application since I am happy with the distrubutor locked at L 10 T -5.

After sorting through 96 wires on the unit, I ended up using 30 of them. This unit can do a 12 cylinder engine with all the added bells and whistles. I added a drive line VR sensor for gauging my speed.

I will be posting data for this on the megasquirt section once I get a reasonable base tune. One thing is really nice so far, the engine starts easy hot or cold. It pops off like a new car. I have set the fuel press to 30 psi and the injector pulses are narrow enough to get dependable starting.

MyT13B

After getting the wires sorted and tailored to the car. I made a box to house the MSP unit and all the extra wires. Playing with the engine free running I was able to iron out a VE table along with a reasonable AFR table. Shown here is the VE table I will use on the first chance I get to hook up my PTO dyno.

I think this should work well as a starting point since free running will not be quite the same as loaded running. From 124 Kpa to 200 Kpa has been guessed at for the first test. I suspect the mid RPM will grow more in the areas that I guessed at. More in the spring............