My search for better performance

[Padgett]

From Canada. Guarantee nothing from memory.

[Ronnie]

Greg Ross

[2seater]

Yup, Canadian and worked in Houma, LA for a while. Called the car Betsy Blue???

[Ronnie]

On 4/2/2021 at 1:14 AM, 2seater said:

Somewhere in there I removed the cat and replaced with a straight pipe. This was about the same time I came upon a flowbench forum that promoted homebuilt plans and techniques. I believed it evolved to be called Flowbench Tech now. I did build a very simple but reasonably powerful bench of my own which I used at first to test things like the stock cat. vs the straight pipe and later a replacement cat. 

What did you learn about how removing the cat effected performance? I've though about replacing mine with a straight pipe. We have no inspections here in TN and I know a guy at a muffler shop who is willing to make a pipe for me. Would doing that increase performance? Or make the exhaust a lot louder?

[2seater]

18 minutes ago, Ronnie said:

What did you learn about how removing the cat effected performance? I've though about replacing mine with a straight pipe. We have no inspections here in TN and I know a guy at a muffler shop who is willing to make a pipe for me. Would doing that increase performance? Or make the exhaust a lot louder?

It does effect the exhaust note; a little bit louder. As for performance, it is hard to judge but I do know the exhaust will smell much like a pre-emissions engine which I didn't like. Unless the rear manifold restriction is removed, likely little will change performance wise. The stock muffler isn't a big problem flow wise at stock power levels. I do have flow figures from the flowbench somewhere which I think I have posted before. What I found to be a decent compromise is to install a modern replacement cat. Nothing exotic or "high flow rated", just a simple Walker or similar. I know they are stealing converters from under cars in parking lots for the rare earth elements but several years ago I know it was well under $100. From memory and relative figures, I found a stock cat around 225cfm, a replacement cat at over 340cfm and an equal straight pipe just shy of 400cfm, at approx one psi.

[2seater]

I have been looking through old photos on my laptops and several different camera memory chips. I must admit I have a confusing jumble of dates and parallel projects over 20 years or so. This makes a sequential narrative difficult and probably inaccurate so, I thought I might try posting some photos I am trying to label rather than a .jpg number with a small note about it. The image quality is highly variable.

 

This the first turbo installation from 2003. The front exhaust manifold design is unchanged except for the rear exhaust crossover pipe coming in from the left. The turbo downpipe connected in the same place as the normal crossover pipe at the rear so that whole turbo assembly could be unbolted from the exhaust connections and the stock crossover reinstalled. The turbo itself is a three bolt style Garrett T3 from an early hot air, non intercooled, Grand National. Note the location of the O2 sensor moved to the front, which I found later was a bad idea as the pre-turbo exhaust pressure can screw up the O2 exchange in the sensor. The compressor blows directly into the MAF/TB. All piping is high heat ceramic coated, inside and out, from Finishline in Milwaukie, OR. I think this is mocked up on my original engine and the engine in the car at the time was the one I rebuilt with a little more compression. This whole assembly was transferred to the engine that was in the car at the time.

 

 

 

This is a top view of the piping layout in raw form from January 2003, a winter project in the heated workshop. The crossover pipe from the rear is on the right and that's an expansion joint in the middle, which is very close to the center of the water pump pulley. The rear manifold was a complete fabrication from new and scavenged stock manifold parts cut up to redirect the rear exhaust to the front. Just peeking out from underneath is the "S" shaped exhaust outlet to the exhaust system. This was bolted to a tab on the new rear manifold so the rest of the stock exhaust system connected normally.

 

[2seater]

        The next idea I tried was what I call a half turbo. Either Saab or Volvo had something like that around the turn of the 2000's. The idea was to do something much more tame and simple at the same time. I reasoned that a turbocharger from a Turbo T'Bird 2.3 liter might just work and I just happened to have a swap meet one. In this fabrication, the front exhaust manifold is cut just downstream of #5 port and the cut off end is rotated to point pretty much straight toward the drivers side. The mating end from the stock crossover pipe is used to feed into the turbine housing.  This is the work in progress from 2010. I have not included photos of my effort to add an inline wastegate for boost control as I discovered there is no need for one and it just confuses the issue. You may notice I am using the MAF/TB integrated assembly from an early TPI intake. It has the IAC located higher up and on the front which allows more room underneath for the turbo downpipe. It is adapted to the stock intake LN3 intake manifold with a 1/4" aluminum plate. The flowbench tested flow rates and MAF response is a good match to the LN3 system and are interchangeable.

 

This view of the same mockup shows the compressor connected to the T/B but I never actually tried it like that. I know now it would have worked fine but somewhere along the line I added an air to air front mount intercooler, so the compressor housing was turned to point straight down where it was routed to the intercooler. A better view of the TPI throttle body and MAF too. At this time I didn't want to repeat the initial lack of good boost control and knock issues. I needn't have worried. 

 

 

In conjunction with the front piping changes, I slightly modified the rear exhaust manifold to hopefully enhance flow from the front manifold and out to the tailpipe. There is also a tapped hole for a pressure tap to check backpressure. Gradually learning the pressure differential of the inlet and outlet of the turbine. This doesn't cure the basic design flaw of the rear exhaust manifold but I thought it might help, turbo or not. This was very early 2011.

 

As I have mentioned previously, I have sort of lost track of which engine was in or out of the car? But I believe this was tested on my original stock engine with the only change being the MAF/TB from a TPI manifold and the aforementioned 1988 camshaft. I almost forgot, it also had 22#-24# Rochester Motec injectors. This screen shot is a recording testing this half turbo setup as described here. I believe this is close to the top of second gear with the MAF registering at the top limit it can read. This setup is almost seamless in operation. There is no big surge, just a little more along the way which builds a little nearer the top. Maybe three psi maximum.

[2seater]

This is a collection of internal and external changes that were done in parallel with the turbocharging projects. I am honestly surprised when I look at the dates of the photos.

 

This is adding the mount for EGR on an early design TPI aluminum manifold. EGR was not used on the first TPI applications but I preferred to have that capability. The passage enters via a slot on the bottom of the intake throat. 

 

These are the heads from the rebuilt engine that I removed due to falling oil pressure. The engine itself had other changes made at the same time, such as decking the block .020" to raise compression to 9.5:1 and tighten the squish distance to approx. .035" for detonation resistance (hopefully) This is also my interpretation of Singh grooves which in theory point air flow too and from the squish areas to the spark plug. The jury is out on that.

 

 

This is an interior shot of the double size intake plenum on a stock LN3 manifold. The idea is to slow pressure rise a little when getting into boost territory. I don't know how much difference it makes but it does look cool. This is the intake presently on my original engine and in the car, more on that later.

 

 

Lastly for now, this is a head being flow tested on my bench after converting the bench from a pitot type to an orifice type. It doesn't matter if anyone knows the difference or even cares, but for my non professional use, it is quicker and less prone to error. Given the apparent simplicity, it has proven to be very reliable and reasonably powerful with close to 600cfm capacity at 28" of water column (about one psi). 

 

 

[Padgett]

L-27 (1992 TranSport) did not have an EGR.

[2seater]

10 hours ago, Padgett said:

L-27 (1992 TranSport) did not have an EGR.

Was that intake plastic or aluminum?

[Ronnie]

I'm amazed at all the time and effort you have put into designing your own parts and fabricating most of them yourself. Especially the exhaust pieces. It must have took a lot of trial and error cutting the pipes to get them to all connect together before welding them. From what I see  you have a lot more patience than I do.

[Padgett]

'92 TranSport still had the metal intake. Think the plastic one began later.

[2seater]

A comment on the photo of the chamber side of the heads above. If you look closely you will see the spark plug side electrode has been ground back to expose more area for the spark. They are not high dollar plugs because they don't get all that much running time. They are just plain old Autolite copper core plugs.

 

I sort of left off with the half-turbo experiment and of course I thought I could make that better? I found I have almost no photos of the second generation installation. The one below is the a good enough example for now. The most obvious thing is the front manifold was a complete fabrication using straight and smaller diameter tubing for the log part. I also purchased a smaller A/R turbine housing for the turbocharger. The stock turbine housing for the Turbo T'Bird is a .48A/R and I installed a .36A/R which is more constricted. The idea for that combination was to speed up exhaust flow and hopefully make the turbo more responsive. I used a different vendor for the ceramic coating that was close to home but the results were less than desired, hence the washed out appearance of the pipe. The other notable difference, not really visible, is this is on the rebuilt engine, actually the second rebuild, after I had the block cut and raised the compression ratio. For reference, that engine pumps just over 200psi on a compression test. It also has the early cast aluminum tuned port "snakes" intake manifold I added the EGR to. The one thing it does not have is the '88 camshaft I installed in my original, but otherwise stock engine. All in all, the results are underwhelming. It does add a tiny bit of boost, but only at higher speed. I don't know if it is the added exhaust restriction, the intake manifold design or the lack of the bit larger '88 cam. It will likely be reconfigured to the original half turbo design but with an '88 cam which I have on the shelf. Possibly may be combined with the latest project still in the works. More on that later

 

 

The next two photos are of the second generation full turbocharger install. The front manifold from the first gen was modified and you can still see the opening where the O2 sensor was, plugged. Works good for a test pressure tap.The manifold was sent out along with the new down pipe for coating. I did away with the ability to remove the assembly and run n/a so the routing could be made better. This is still the original turbocharger, but it is rotated 90* so the air inlet for the compressor aims pretty much in the area of the stock air box. This only shows the turbine housing in place as it was being assembled. The mushroom shaped thing below the throttle body opening is the divorced Turbonetics wastegate. This one works very well and doesn't allow boost to creep. The throttle body is the enlarged one I had made years earlier. There is no MAF visible because it is also a divorced inline style 3" in diameter and deserves it's own topic. The O2 sensor was moved to the downpipe near the throttle body.

 

This is the engine now in the car, and is the original with about 100k miles on it. The heads are a pair I got for free from Daves89 which were on a 5k mile engine which unfortunately had water get inside when stored. The intake ports were rusty and a couple where the valves were open, extended to the block as well. I did my usual mild port and cleanup, replaced all the intake valves and installed on my original engine using FelPro headgaskets to drop the compression ratio to calculated 8.34:1. I have posted about them before but I will reiterate that the bore diameter of the FelPro's are way too large and they will lower compression ratio as well as add crevice volume that does little for power except fill with carbon. In this case, I wanted to lower compression ratio to better suit the intended turbocharging.

 

 

[2seater]

Just a single image here of the engine as it sits in the car today. To synopsize, it is the original engine at about 100k miles, with cleaned up and ported '88 heads from Daves89. It has a used 1988 camshaft but aside from the head massaging, is totally stock. The intake manifold is a welded up fabrication my good friend who teaches welding assembled on a stock LN3 base after the plenum was cut off. The top is removable. The throttle body is stock but was enlarged several mm by a guy in Iowa who did so for GN customers. The cruise control servo is mounted to the crossbar to the strut towers. Relocated and fully functional to make room for the turbocharger and wastegate. The vacuum football is slid back by the master cylinder for the same reason. There is an oil pressure gauge installed in oil pressure feed to the turbocharger, which contains a .060" restrictor to avoid flooding the turbocharger with too much oil. The upper radiator "hose" is 1.25" copper pipe that has been welded by my welding buddy. He used copper wire from a piece of romex house wiring as the filler. The intake pipe on the right side comes up from the front mounted air to air intercooler through the opening where the charcoal canister used to be. The ignition module/coil is the stock Magnavox style but rotated 90* to clear the exhaust crossover pipe from the rear exhaust manifold to the front. The yellow colored fuel injectors are 30# from Accel.

 

The MAF is inline directly to the rear of the turbocharger in this view. This a 3" MAF which I believe is from a 3100 Chevy engine. I received this one from Ryan at GM Tuners for helping him with flowbench vs frequency output. In rough terms, it flows 50% more air at same MAF frequency output vs the stock LN3 MAF. It isn't linear and is very close to stock output at idle flows so it has a stable idle. It is one way to expand the flow capability yet keep the reading within the ECM's ability to read it and allow a larger tuning window. You may notice there is no boost dump valve. There is precious little room for one and I don't believe I run high enough boost to require it. It is sorta fun to jab the throttle a little and let it snap shut at a low speed roll. The boosted air has nowhere to go and backs up and out through the air filter and makes a whickering noise, like an extended sneeze. Childish I know.  

[Ronnie]

1 hour ago, 2seater said:

A comment on the photo of the chamber side of the heads above. If you look closely you will see the spark plug side electrode has been ground back to expose more area for the spark. They are not high dollar plugs because they don't get all that much running time. They are just plain old Autolite copper core plugs.

I did something similar when I was racing motorcycles on alcohol. I didn't cut it back like you did. Instead I filed it more to a point on the end which makes it easier to fire under high compression. I reduced pinging under heavy loads at low RPM as well improving throttle response. Engines running on alcohol need more ignition timing and larger jets. The ignition systems back then were marginal so doing what you could to make the plugs fire more easily was helpful. I didn't have to file the electrodes to a point after I discovered the  U-gap plugs that already had more sharp edges on the electrode to make them easier to fire. I wonder if they still make the U-gap plugs? Since ignition systems have improved so much with the electronic ignitions systems electrode modifications and U-gap type plugs may no longer be helpful or needed.

[Ronnie]

BTW, I didn't file the electrode to a sharp point on the end. That would contribute to pre-igntion. I just filed them so they would have more sharp edges. They still had a smaller flat on the end of the electrode.

[2seater]

1 minute ago, Ronnie said:

BTW, I didn't file the electrode to a sharp point on the end. That would contribute to pre-igntion. I just filed them so they would have more sharp edges. They still had a smaller flat on the end of the electrode.

They are kind of a pain to screw around with. The material is hard and it is easy to mess up the center. I don't know if any of the theories or fancy plug electrode shapes make a darn bit of difference or not. I am not interested in  longevity because of the rapid turnover but looking for magical plugs for a hobby car does make me smile.

[Ronnie]

You should give some of these a try just as an experiment. They aren't expensive. Would be interesting to know if they would make a difference in your turbo engine.

Spark Plugs | OE Type | Original U-Groove - DENSO Auto Parts

[2seater]

27 minutes ago, Ronnie said:

You should give some of these a try just as an experiment. They aren't expensive. Would be interesting to know if they would make a difference in your turbo engine.

Spark Plugs | OE Type | Original U-Groove - DENSO Auto Parts

Okay, thanks, I will look into that. 
 

Racing motorcycles on alky sounds pretty hardcore and a story in itself. Much more serious than anything I have ever done.

[2seater]

     The photos below are of a 3.8 liter head from a Grand National and a 3800 head from and LN3. Flow testing of both heads on my bench shows essentially no difference in the flow potential of either head. Valve sizes are exactly the same. The LN3 head does have slightly better exhaust flow, partly from a better shape of the port and also because the port is shorter in length. The GN does use a high temperature resistant inconel exhaust valve and there is supposed to be a reinforcement in the head to support the flat chamber shape.

 

The GN head is on the left in all photos. Note the GN head chamber is more broad and flatter. The spark plug on the GN is almost straight down where the LN3 is angled toward the exhaust valve which is generally desirable. The GN chamber also has that small recessed are opposite the exhaust valve, the purpose is unknown other than increasing the volume of the head. Both heads use the Buick 10* valve angle. Chamber volumes are similar and do vary a little but average 35.5cc

 

 

This is the valve cover view. The GN uses a rocker shaft which bolts down to the three pedestals cast in vs individual but non adjustable rocker arms. Spring pressures are very similar, approx 75-80# closed and 210-215 open.  The difference in exhaust face and spark plug angle is readily apparent.

 

 

This is the exhaust face of the heads. The GN is rectangular and LN3 is "D" shaped. The GN exhaust port extends outwards from the head itself where the LN3 is essentially flush with the outer body of the head. This makes the LN3 a little more compact and the port spacing is the same.

 

This is the intake face and the port dimensions are very similar with minor differences in width and height. The black rubber around the center ports are the remains of a bellmouth applied for flow testing. The one major difference is two of the intake ports are side by side on the GN where the LN3 are evenly spaced. This difference coupled with the LN3 block being slightly longer to get the cylinders on center, makes the heads incompatible although they would physically bolt on.