The History of My Car & Engine

from Rally Bashing Hack to Weekend Racer

STAGE 12 - G180 EFI Turbo - Big Everything!

This will be the final stage of development for this engine (I think??).  If I wanted more power after this, then I may as well fit a bigger engine, such as a quad cam V6 or an alloy V8 and work that over.  This combo should be enough for 10 second quarter mile times, and will probably be too much power for the circuit racing I want to do, but I am sure it will be a fun ride!

I decided to bite the bullet and buy some forged pistons.  After shopping around for a while, I came across an engine package that seemed like a pretty good deal.  The new engine, a G180, came as a bare block with a bunch of parts in boxes.  

Block

The block's been bored to fit 87mm pistons (2 litre pistons).   So this engine is the same displacement as a stock G200 (G180 and G200 have the same stroke).  The block has been o-ringed to help seal against the head gasket under extreme cylinder pressures, internally de-burred and painted to improve oil flow back to the sump, the rods have been linished and shot peened to reduce high stress areas, and the crank has been cross drilled for extra oil flow to the bearings.  These last three mods will allow more reliable high rpm operation.  Here are the block, crank, pistons, etc, being assembled.

I have since assembled the engine with the modified head (see cylinder head section below) so I can verify the performance improvement from the mods detailed in Stage 11.  Once completed, all the components listed in this section will be bolted on.

Pistons:

As I said above, the block's been bored to fit 2 litre size pistons.  The difference though is the pistons are forged SPS items.  Even though I know that a cast piston will handle the power, and both cast and forged pistons will die with detonation, my time is more valuable to me today, and I don't want to waste it rebuilding engines when a water line breaks, or something similar.  A forged piston would probably have survived that incident.  I am also running Total Seal gapless rings to retain the high cylinder pressures, 

These pistons have oil return holes instead of slots.  The slots in most factory pistons cause weak spots where the high stresses from detonation will cause cracking.  By simply having holes, the piston is a stronger unit.  Obviously, being a forged piston means the base material and design is stronger as well.  The pistons have a small dish with valve reliefs to suit my high lift cam.  You can see the linished and shot peened rod in the photo above also.  There is normally a seam from the casting process of the rods, which is removed to avoid any areas where stress concentration can occur.  This allows the rods to be used reliably at higher power levels.  I have never had a problem with the stock rods, but I have seen many engines where a rod has broken and punched a hole through the side of the block.  Not a pretty sight.

Cylinder Head:

I have done a lot of development with the cylinder head and manifolds on a flow bench (thanks Andrew).  I had 3 different cylinder heads flowed;

1.  My old TD 1600 big port, big valve, high compression head.  This is the sought after head that most people refer to as the TX head, I have found them fitted on TX's to TD's from factory.  Fitted with 42mm inlet & 34mm exhaust valves.  I had spent a lot of time porting this head, blending the valve seats into the ports, un-shrouding the valve area in the combustion chambers, and basically trying to direct the air flow at the valve over the last bit of length of the port.  It has also been shaved down to the valve seats, giving 40cc chambers.

2.  My current turbo head (TG pollution head with low compression big chambers).  I got this head flowed to see where it was at, whether it was worth keeping and doing further work on, and where the improvements can be made.  Being a pollution head, its the one with the air pump ports at the top of the exhaust port outlets.  These heads have smaller ports with a sharper turn in the port bowl area than in head #1.  The smaller diameter port means air velocity will be a bit higher, so flows at lower valve lifts might be higher, but as flow increases, velocity increases, and so does the friction of the air on the port walls, which will limit the peak flow figures. 

I wanted to stick with this head because I wanted to keep the compression low, however I was concerned that I simply wouldn't get it to flow as much as head #1 due to the poorer inlet port design.  These heads are originally fitted with 40.4mm inlet valves, but I had the seats machined out to suit the 42mm inlet valves from my TD head.  The exhaust valves are the same.  I did the exact same porting as I did with head #1, probably spent more time overall on it trying to do a better job, as I was aware the ports are smaller than those in head #1.  I also removed a bit of material from the chamber to get the compression even lower.  The chambers are now 52cc.

3.  Stock G200 head.  This head has the same size valves and ports as a TE or later G161 head (from what I can tell).  I also got it flowed so I could get a baseline of where a stock head is, and what sort of improvements I have made when porting my other two heads.  I didn't' have a stock 1600 head to flow, but I think this one would be very similar.  Valve sizes are 40.4mm inlet, and 34mm exhaust.  Combustion chamber size is about 58cc.  So this head is basically the same design as head #2 above, but in stock standard condition, no porting, no bigger valves, and it doesn't have the air pump inlets in the exhaust ports.  As its from a G200, they also have larger chambers to keep stock compression ratios under 9:1 with factory flat top pistons.

All testing was performed at 28" of water.  Measurements were taken in 50thou valve lift increments.  Out of interest for some people, what I have recently read is that if the flow measurement is done correctly, it doesn't matter what the level of vacuum or suction (i.e. 28" of water) is used to do the test, as the calculated flow should be the same.  Typically, the greater the suction, the more accurate the results.  Below are the results for the inlet ports:

As I predicted, head #1 is out-flowing head #2.  Luckily for me, both heads #1 and #2 outflow head #3, as if they didn't, it would mean I can't port to save myself.  There are heaps of interesting things to note from these results though:

This has given me some good news to work with, as now I know I am not hurting performance by using the pollution head #2 on my engine.  In fact, if my cam only provided valve lift of up to 300thou, head #2 would make the most power.  However, my cam has a lift of 420thou, and I would like to increase the flow in the 300-400thou valve lift range to at least try and get it closer to the flow of head #1, which would make head #2 definitely flow the most overall.  Because of the lift of my cam, and figures measured over 420thou of lift are irrelevant to my engine, but are still of interest.

These are the results for the exhaust ports:

These exhaust port flows are also surprising.  All three heads have the same exhaust valve size (34mm), but I spent a considerable amount of time on heads #1 and #2 to try and increase their flow.  Obviously it hasn't had a huge impact.  This would lead you to think that if you are trying to save time or money, don't bother playing with the exhaust ports, as there is very little gain to be had.  If you read on, you will see that this is not the case. 

Since I needed a low compression head and I had already invested so much time in my current turbo head #2, I decided to see how much more flow I could get out of it.  Increasing the flow is to be achieved by more extensive porting and bigger valves.  Head #2 has received some bigger inlet valves and seats from a Commodore V6 Ecotec engine, the valves stems are cut down to the same length as the Gemini valves, the valve size is now 46mm up from 44mm. 

I have also fitted some bigger exhaust valves keeping the standard exhaust valve seats but machining them out to suit the larger valves.  These valves are off the shelf Isuzu 2.3l 4ZD1 exhaust valves and are 36mm diameter, up from 34mm.   The photo below shows the larger valves and how the valve seat to combustion chamber is a smooth transition.  This is what is mean by unshrouding the valves.  Usually there is a sharp step/ridge next to the valve seat caused by machining the chamber to accept the valve seat.  Removing this sharp ridge improves airflow into the combustion chamber when the valve opens, and out into the exhaust port.

Then some more porting has been done to make this head flow enough to utilise the larger valves.  The graph below of the flow figures tells the story.

I am very happy with this result.  It looks like a different head now with massive flow gains right across the range of valve lifts.   Once again though, it hits a bit of a wall at 300thou lift.  The again means the port is the restriction, but the port walls are very thin now from so much porting, and we have already made a hole in one port that needed to be welded up.  As my cam only lifts to 420 though, I probably wouldn't benefit much from more flow right at the peak valve lift areas, as the valve is only open for a very short time at peak lift, so the peak lift figure is not that critical. I believe the lower lift areas are more important as the valve spends more time on those areas during the intake stroke of the engine.  So unless I fit a bigger camshaft, I think the current flows at the respective valves lifts will be great.

Its interesting how changing angles within the port and a common sense approach to where the air will flow can dramatically improve the flow of a port.  I would recommend anyone who is serious about making power should get in touch with an experienced head porter with access to a flow bench.  If not, its all a bit of a guess, and although you may make good gains, you wont get all the gains available.

The bigger exhaust valve has given a great flow improvement simply because the valve on exhaust ports are usually the biggest restriction.  This is shown by the constant rise of air flow as the valve is opened further.  When you think about it, the exhaust ports are similar in size to the inlet ports, but the exhaust valves are around 20% smaller.  Therefore simply increasing valve size makes a big difference, and often the ports themselves don't need to be touched, as the port has the potential to flow a lot more than what the valve will let through.

So my turbo head (#2) has not only equalled the flow of head #1, but its gone way past it.  Head #2 has gained a lot in low lift flow figures, which is the most critical area, and also achieved peak flow figures of 45% greater than a stock head.

Turbo:

Next on the list of upgrades is the turbo.  I have bought a new turbo which is a fair bit bigger than the stock commodore T3.  Its a T3/T04E hybrid running a 56 trim T04E compressor wheel and stage III Turbonetics turbine wheel, with a 0.63 A/R T3 exhaust housing.  This will have the capability to flow in between 400 and 500hp, and should easily get me to 300-350hp @ wheels.  I kept it internal waste-gated for manifold simplicity, these power levels can be achieved without the need to go to an external gate.

You can see the high flowing Turbonetics turbine wheel below, its less aggressive than your typical OEM turbine wheel, which means the air doesn't hit it as hard.  The downside is more airflow is required to make the turbo spool up, the upside is there is less flow restriction, so overall power will increase.  For a circuit racer, you find that engine rpm is usually pretty high all the time, so turbo lag is not a huge issue.  Its often the case that the engine rpm is high enough that as soon as you open the throttle, the turbo will boost almost instantly.

This photo shows the compressor size compared with an RB20DET turbo, which is of a physically similar size to my VL turbo.

Plenum Chamber:

I have made a custom plenum chamber so I can mount the TB at the front, instead of locating it over the rocker cover.  This will allow more direct air flow into the plenum, instead of the induction piping having to snake up over the engine and rocker cover, reducing friction losses.  The plenum is also big, at around 4 litres, it should be a good thing.  It also has bell mouthed entries to each inlet runner, unlike the stock Rodeo plenum with has square edged entries.  This plenum arrangement flows more air, showing a 10% flow improvement to each cylinder on the flow bench.  That's with the stock Rodeo throttle body.  I can also mount a larger throttle body if I need to like an XF unit.

PIC OF PLENUM

Exhaust Manifold:

Since the piazza turbo manifold is suspected of being the bottleneck of the combination, I have decided to have a new manifold made.  Although the piazza exhaust manifold has been shown to flow enough air, I'm aiming for a manifold with smaller than average pipe diameters so the turbo is hit hard and boosted up quicker.  Obviously not too small or else overall power will be affected.  This is important as the new turbo is bigger that my last one, and I don't want turbo lag to make the car unpleasant to drive.

In the mean time, I have fitted a high mount custom manifold made from steam pipe bends, with much better flow characteristics than the piazza manifold.  The piazza manifold is the almost a "log" style, there is almost no directional flow, it simply provides a mounting for the turbo and passage for exhaust to reach the turbine.  Cylinders #2 & #3 are directed towards the turbo, but the manifold incorporates very tight bends and the exhaust gasses from cylinder #1 run directly into the exhaust gasses from cylinder #4, head butting each other.  

This photo shows the underside of a standard piazza manifold fitted with the original turbo.  The factory piazza dump pipe can also be seen.

The manifold I have fitted has the exhaust gas from each port aimed at the turbine inlet, the exhaust pulses don't combat each other as they do with the piazza manifold.  This should improve overall flow and hp.   

I am using this manifold to verify the performance improvement from the mods detailed in Stage 11.  If it turns out to be a good performer, I may use it to mount my big turbo, otherwise I'll get a manifold made.

Well........... a few years later.............Feb 2008

Well it turns out that this manifold above has given a 30hp improvement at the wheels, for details check out stage 11.

Intercooler:

The other major mod is a larger front mount intercooler.  I had been trying to decide between a water/air unit, or just a bigger air/air unit, and air/air is more simple, with less maintenance, so I will go that way.  The RX7 unit is probably getting maxed out with the current levels of flow and inlet temps.

I purchased a cheap hybrid style front mount that will fit in front of the radiator without too much hassle, core size is a fair bit bigger than the RX7 cooler, so it should keep temps under control.  I will put it on the flow bench and compare it to the RX7 cooler before making piping to suit in case its a step backwards.  If so, I will have to look at a good brand name front mount such as PWR, etc.

Interior:

I am also improving the interior a bit, it started with some new black carpet, now I have a pristine black dash to go in, and have fitted a pair 300ZX electric seats, trimmed in yellow leather.  These seats are pretty easy to install, just need the standard 300ZX rails modified a little bit.  The width of the gem rails is the same as the Nissan.  These suit my harnesses well too.

These new bits of hardware, combined with my new exhaust and cam should make for a really fun ride. indeed, with an aim of 300-350hp @ wheels (250kW @ wheels).  That should be plenty for a 900kg car.

LAST UPDATED 24/7/08