The History of My Car & Engine

from Rally Bashing Hack to Weekend Racer

STAGE 11 - G200 EFI Turbo - Big Cam & Exhaust

I fitted a Wade turbo cam, which was a surprising improvement.  I have fitted cams to engines before, and often its hard to really define where the extra power is.  A new cam billet was not available, and I was in a hurry, so I ordered the biggest cam I could get as a regrind.  This cam increased mid-range power a lot and the top end a little bit.  The Mid-range improvement was like night and day, a lot like running more boost, just like the power increase I got when I fitted the intercooler.  The top-end power gains were also noticeable, but not as dramatic.  Probably everything else is holding it back now, like exhaust, turbo and cylinder head.  

I then fitted some new intercooler to throttle body plumbing and a blow off valve.  My old plumbing was a mis-match in internal diameters, with heaps of rubber hose joined sections.  This would have caused a fair bit of turbulence and restriction.  The new plumbing is all 2.5" pipe with bends cut from a donut, which is like a continuous mandrel bend, but you just cut sections from the donut to make the angle of bend you need. 

In an attempt to increase the efficiency of my intercooler, I painted the cooler black and added some air guides.  Black is the best colour for heat transfer, however I'm not sure if the coating of paint acts as insulation and this cancels out any benefits of the colour itself.  

The air guides are to increase the pressure immediately in front of the core, forcing more air through and increasing the cooling effect.  You may notice that the guides are pointing inwards, opposite to a normal funnel.  This is intentional, as a higher pressure level is achievable this way.  I have not done any temp measurements to see what difference this has made, might be a couple of hp. 

I then went down to Phillip Island for a day of circuit racing.  Phillip Island is one of the best race tracks you will ever see, its very fast, and you take some sweeping corners flat out in 5th gear at about 5-6000rpm.  Around 200km/h anyway.  Once again, I hadn't been to the dyno for a while, and was only running about 15psi boost, with a conservative (rich) tune just to be safe.  

One of my coolant lines for the turbo was rubbing on an engine mount, and sprung a leak.  I thought I could hear some detonation as some stages of the racing.  With the engine roaring, and your helmet on, its pretty hard to hear anything.  I started to lock up my front left wheel when braking, I since found that coolant was getting on the tyre, causing it to slip.  

By the time I saw my water temperature was over 100deg C on the Microtech handset, it was too late.  I had lost a heap of water, the excessive heat had caused some detonation, and I had broken some pistons.  I now have the Microtech running a temperature warning light, and I recommend every racer use one.  It would have saved my engine, but I was running a shift light at the time.  The Microtech version I have only has 1 programmable output.  Its either temp, boost, or revs, or a combination.

So I drove home all upset, (yes it still drives pretty good with a blown motor, just lots of blow-by).  This motor just doesn't like my engine bay!  After a few months of sulking, I decided I needed a new exhaust system.  

The old restrictive pipes had to go.  So I used the existing 3" dump pipe and continued it back to up and over the diff.  I then branch off into a pair of 2.5" tailpipes, and have a stainless muffler under each side of the boot floor.  When it was at the panel beaters getting the new rear quarter and beaver panel, I got the boot floor modified on the passenger side so it has a recess for a muffler, just like the drivers side.  

The exhaust took a long time to build to make sure it cleared the diff under all conditions, and that the mufflers were equally spaced and looked right from the rear.  A lot of people warned me about the pipe clunking on the diff, particularly when a gem is lowered, but if you do it right and hug the floor as best as you can, you shouldn't have any problems.  Its all mandrel bent, and it has several flanges so I can unbolt sections.  Should be good for a few more hp.  Just have to rebuild the engine.

With the new 3" exhaust, bigger turbo grind cam, and new intercooler plumbing, I am hoping for 220-230 hp @ wheels at the same boost level of 19psi.  As soon as I build the new engine, I will report the dyno figures.  I am only guessing, but I would think this combo would do an 11 second quarter, especially with the LSD and my race tyres for grip.

I plan on one more stage of development, as discussed in the next section, but before I get there, I will assemble the engine how it was before it blew, with the bigger exhaust to see how it has improved on the dyno.  The only difference will be I have done a lot of development on my cylinder head, which I will have to fit.  This is all described in the next section, but I will come back and update this one.

Well........... 2 years later.............2005

After building the G180 as described in Stage 12, but with the same induction and turbo combination as before, the only difference to this new engine compared with before is that I have fitted the heavily ported head and bigger inlet and exhaust valves.

Compared to the last dyno run when the car made 197hp @ wheels, this combo has the big turbo cam, the 3" mandrel bent exhaust, better intercooler plumbing, and the much better flowing cylinder head.  I went to a different dyno this time, I used Dalton Automotive in Geelong.

Dyno run # 1: (2005)

It made 192hp @ wheels.  (143kW @ wheels).  

That's right, after all those power making improvements, I actually went backwards in hp.  The first thing I should point out is that its a different dyno, and they said that the dyno I used previously had consistently given readings slightly higher than theirs, but not that much!  

The theory put forward is that my piazza exhaust manifold is simply an airflow bottleneck, as they have seen very similar set-ups to mine make more power, but with a custom exhaust manifold.  

I drove the car home, and decided that a manifold swap was needed to make sure it was the problem.  I had a few custom manifolds lying around, none of them were exactly what I wanted, but one was pretty good.  It was a sort of high mount made from steam pipe bends, and it had much better flow characteristics than the piazza manifold, and that was the main thing.  The photo below shows the new manifold and the turbo mounted up higher.  

Unfortunately, almost as soon as I had it fitted up, I had a coolant leak in one of my cylinders, I suspect its the thin walls of the inlet ports, one has cracked allowing coolant to be drawn straight into the cylinder.  I did have a short drive before it happened and was amazed at the different and strange turbo sounds I could hear with the new manifold.  I am still to remove the head to investigate further.

Well........... another 2 years later.............Feb 2008

I had finally gotten round to pulling of the head to find 1 inlet port had a small crack which was letting coolant in.  Had the crack welded up and smoothed out the repair, and the head was re-fitted.

Back to the Dalton Automotive dyno in Geelong and started to spin the rollers.

I had a feeling it was about as quick as it used to be, but I had the boost back on 15psi just to be safe until I could get the mixtures checked again.  So with exactly the same engine combo as the previous dyno run, except for the different exhaust manifold.

Dyno run # 1: (16-02-2008)

It made 187hp @ wheels.  (140kW @ wheels).  

Not bad, pretty much what it made last time, but it was only 15psi, so had to wind it up some more.  Also the mixtures were a bit lean.  So the Microtech handset was getting its buttons clicked and some more fuel added in.  The engine also wasn't revved right out because was a bit lean.

Dyno run # 2: (16-02-2008)

It made 198hp @ wheels.  (148kW @ wheels). 

Picked up quite a few horses with a mixture tweak.  The extra air flow from the new exhaust manifold has effectively leaned out the mixtures, so had to add some more fuel under boost to get the a/f ratio back to around 12.5:1.

Dyno run # 3: (16-02-2008)

It made 205hp @ wheels.  (154kW @ wheels).  

Now that's more like it, and only a 1psi boost increase.  We wound it up a bit more because I wanted to run around 18-19psi, as that's what I ran with the previous engine combo in stage 10.  

We also checked if the air filter was being a restriction and pulled it off, only to find a piece of electrical tape across the pipe opening that leads to the compressor housing.  This was blocking airflow, and removing it along with the boost increase showed a good power gain.

Dyno run # 4: (16-02-2008)

It made 217hp @ wheels.  (162kW @ wheels).

Boost was spiking at these air flow levels, it would hit 20 psi and then drop back to 18psi which is where peak power was made.  The turbine housing being the suspected culprit in limiting boost, with the turbine wheel simply not flowing enough air to spin the compressor any harder.  This was maximum boost, it didn't matter how the bleed valve was adjusted.

The suggested fix... an external wastegate.  But I have my new bigger turbo to fit up, so will see how that performs.

This power level also shows that having a piece of electrical tape covering up part of the inlet pipe going to the turbo compressor will restrict air flow.  What a surprise!

So we stuck the air filter back on just to see if the filter element itself is a restriction.

Dyno run # 5: (16-02-2008)

It made 216hp @ wheels.  (161kW @ wheels).

Only a 1hp loss with the Finer Filter pod, not too bad at all. 

So with roughly a 30hp@wheels gain since the last dyno session, and the only modification being the different exhaust manifold, its clear that this new one is a better design.  If you're chasing about 200hp@wheels (150kw@wheels), then the piazza exhaust manifold will do the job, but if you're after more power, you'll have to lean towards a custom job.

You can see the difference in the two exhaust manifolds, the photo below shows my modified cast iron piazza manifold, which is pretty much a "log" design where the runners for ports 1 and 4 head-but each other at the collector, and there is no real directional flow into the turbo exhaust housing.

This the the new exhaust manifold below.  Its not exactly what I'm after, but the performance its giving right now is pretty good indeed.  The extra 30hp at the wheels is due to the improved directional flow towards the turbo flange.  

So the next step is to get a flow bench comparison on my intercoolers, and to bolt on the big turbo and chase some more power.

Check out STAGE 12 - G180 EFI Turbo - Big Everything!