Pitts S1-SS

So Gary called to confirm the horse power rating from our engine runs was 212HP. I’m well pleased with that. This was a standard o-360 rated at 180HP at 2700, and it’s been boosted by 42HP due to the 10:1 pistons and cold air induction system. I’m not sure how much power the TBI adds (nothing I think) and this is without the 4-1 exhaust which I believe will only add power through the midrange. I’m pretty happy with this.. I really wanted to get 200HP+ out of the engine, and I’ve achieved that, so the S1 should perform well.

I went to the engine shop this weekend just to lock wire all the fittings – fuel pump, oil relief valve, dip stick tube, Vernatherm, etc. Didn’t take long. No pictures. I also made an engine plate extension with the words “EXPERIMENTAL” on it which fits under the standard engine plate, and fitted it onto the sump. Not sure how it works here in NZ, but the engine keeps the same plate, with o-360-a1ad on it still, even though it is very definately no longer this.

I suppose I would call it an XIO-360HC if I had to make something up. HC for High Compression pistons, X for Experimental. Not sure about the I.. it’s a TBI not individually injected cylinders, so not sure what nomenclature to follow there. I’ll check with the regs to find out exactly what I need to do to label it.

Time expended: 3 hours. Total time: 1182 hours.

Sunday, and time to remove the engine from the test rig and start the process of pickling it for a while until the Pitts is ready.

Thoughts on the TBI… well, wow, I was impressed honestly, I was expecting problems. Maybe I was just expecting us to fiddle to get it to work correctly as the shop deals with std carbs and injection systems all the time, and never with TBI’s, but it was simple and straight forward. Maybe that’s more credence to Gary than anything, but it did seem simple, and effective, and starts on a dime, as you can see from the videos! I’m sold.

Tomorrow – time to dismantle everything and get the engine ready for pickling until my Pitts is ready.

Time taken 6 hours. Total time: 1178 hours.

Gary filled the engine with hot oil and we got the truck ready to drive out to the apron. I meant to make a note of the oil we used, but it is obviously a grade that is for running engines in and seating the rings etc. I’ll check next time. Once on the apron, Gary stayed in the truck and I jumped out with my video camera. Honestly, I was dubious it would start. I pressed the record button and called out OK and he hit the starter. By the time the videocam started recording, it was already running. I got such a suprise when he turned it over and it took on the second turn of the blade! In fact it happened so quick I missed the first 2 seconds on my video camera. Darn. Anyway, I got all the rest of the starts from before the blade, so that’s ok. In summary she fired right up as if she’d never been torn down and rebuilt. Amazing. I was very pleased and relieved.

All in all we did 4 engine runs according to test regime that Gary followed. The first slowy built up from idle to 2400 RPM and then stepped down. During this Gary noted the oil pressure was a little too low, and so after the first session we pulled the truck back into the hangar and pulled off the oil relief valve. It has two washers in it so he added another three, and we continued onto the second run. We also spotted a small oil leak on the back and found that I hadn’t tightened one of the plugs closing off the oil well. So we tightened that, and went back out. In the second session, the oil was a little high, and so we took one washer out to leave 4 washers in the relief valve. THe rest of the figures all looked good. The temperatures and pressures were stable and well within center of the range.

We then took the truck out to the sound proofed area near the Tower and did the main engine run. Stepped it up again, recording all the way, and then let it run at full throttle for 60min taking readings every 15min. The noise was quite deafening even through the earmuffs, and Gary hopped out after the first few minutes whilst in the early step up stages and left me to step it up to max and do the recordings. About 30min into the long run, one of the CHT’s must have fallen out since the Temp dropped to 23C/73F. That caught my attention, but a quick jump out the truck and I spotted the culprit. I just let it run, the other 4 cylinders were all pretty close to each other, sitting around 140-150C/284-300F. What I did notice is the max RPM was achieved of only 2500 RPM and at a manifold pressure of 28.5″. I’m not sure about the MP, but that seemed low on the RPM, but when Gary got abck he explained the heavy prop/hub on it was pitched too coarse, so on the final test run, the 4th, he reset the pitch slightly. We also took off the air filter. I have not intenton of running a suffocating filter on my engine, so this is more indicative. The final run was a blast. 2850 RPM sounds hideously loud from a few feet away! I thought I was used to big sounds, as I used to have an M14P on my Yak, but this thing was still quite deafening. Viscious even. Just how I like it

I’ll collect the data from Gary later, but he seemed happy. I’ve posted a few videos here, some are big, but the clip of 3rd run is short and fairly indicative of the rest, so the one to watch.

Truck driving off to apron, 13sec, 5MB.
First run – first 500 seconds, 200MB
First run – last 80 seconds, 27MB
Second run – first 600 seconds, 200MB
Third run – first 30 seconds, 12MB    ** best one to watch, short, with quick start **
Third run – inside the truck, 14MB
Third run – midway 30 seconds, 10MB
Fourth run – Gary inside the truck, 45sec, 15MB
Fourth run – midway 150 seconds, 52MB

After all this, I was pumped, and we went back to the shop to examine the engine. First we checked for leaks – everything ok. We drained some oil from the filter – it was a greeny colour, but nothing in it, which was good. We removed the oil filter completely, cut it open and examined it, no fragments of anything, so Gary was pleased. We then did a blow by and compression check on each cylinder. All were 80/77, except one which read a bit low – 80/68. Gary thought it might be some carbon under the valve since we were buggering around with idle a bit to play wth the Rotec TBI, so we’ll check it again after a few more hours to see if it has come back to normal. But overall he was happy, and so was I.

Thoughts on the TBI… well, wow, I was impressed honestly, I was expecting problems. Maybe I was just expecting us to fiddle to get it to work correctly as the shop deals with std carbs and injection systems all the time, and never with TBI’s, but it was simple and straight forward. Maybe that’s more credence to Gary than anything, but it did seem simple, and effective, and starts on a dime, as you can see from the videos! I’m sold.

Tomorrow – time to dismantle everything and get the engine ready for pickling until my Pitts is ready.

Time taken 6 hours. Total time: 1178 hours.

Big weekend, and a major milestone in the build finally reached.

I was at the shop early on Saturday morning (6:30am). Gary had already had the engine hoisted off the stand and onto the back of the truck. He has this ancient truck for testing engines and doing break-ins, and it has a test bench on the inside from where you run the engine. We spent the whole morning connecting things up and double checking everything. First, I put the exhaust stack on. He has straight pipes for testing, so they went on easily. We planned to also run the Raven 4-1 exhaust and compare them. Next we put new spark plugs in (only had three, so dug out some good condition used ones which I had to sand blast and polish up for him). The dualmag had also been put on previously, so it was just a case of connecting up the leads. I ran the leads through cushion clamps as per standard practice, and then we put the temporary cowling on.

Next up we connected up all the various oil and fuel connections on the back, including the CHT leads to each cylinder, and oil pressure, temp and manifold pressure. Gary takes an additional oil pressure reading from the front of the engine, so we plumbed that in as well. We put the Vernatherm in, hooked up the Tacho, and put on a short pipe to act as the breather. On the sump I installed a drain tap, and then connected up the starter motor. No need for the alternator to go on at this stage. Finally, Gary inspected the internals of the fuel pump, declared it nice and clean, and he put it on for me.

Next up was to figure out the Rotec TBI. I brought the installation guide and pile of pictures off the web, but I’ve never seen an installation on a forward facing sump setup, so I knew it would require some planning. Gary took it in his stride and worked out a jig to hold the throttle cable, and we fed it in from the left side. We then played with the throttle in the truck to make sure we had full throttle travel. The mixture control was easier, although we had to shift the pivot arm around a bit to get an angle that worked. I’m not sure this is how I will set it up finally as I will need a bellcrank or something to make the turn to the throttle as the cowl will be tight. I also need to figure out how to put the regulator on in this configuration. The sump is right in the way of where the regular fuel tube will need to come out in order to meet the “same level or higher, and no “further than 6 inches from the TBI” rule. Gary had a read an interpreted the instructions that the 6″ rule applied specifically due to gravity effects on the regulator, and we should be fine to run a longer tube to the back and just connect the regulator to the fuel pump. I was dubious, but it looked like it would take time to sort out an alternative fitting, and we were chasing the clock a bit to get the run ups down today, so I went along with it. Turned out fine in the end, but I’ll check with the factory in Australia about this, whether it can work for normal ops too – or only in the test rig.

I installed a spacer onto the TBI in order to take a tube and airfilter, and put those on. I wont have an air filter, but will need to work out something so I dont ingest runway debris and dust.

Next up it was time to heat the oil and fill the engine. Gary has a portable oil heating drum thing. I took a few shots of his truck and test rig.

We then took a lunch break to let the oil warm up and prepped the paperwork for the run ups. Exciting!

Time taken 6 hours. Total time: 1178 hours.

Back at the APS engine shop today, and it was a fun day as I got a lot done. First up was to prepare the intercylinder baffles for reinstallation. I had painted them last time but the cylinder fins had bitten a little bit into the soft aluminum of the baffles (quite common) and the repair for this is to use Araldite glue to fill the dents in flat. Then we covered the baffles with red RTV to prevent vibration against the fins. Looks messy but is ops normal in his shop. Whilst this dried I started putting the original chrome rocker covers on. I had use blank rocker covers during spraying, and so took them off, cleaned the paint off the silicon gaskets with thinners, and installed the shiny rocker covers. Torqued all painted bolts to 25 inch/lbs. Book says 50, but this is for cork gaskets, and Gary prefers 25 inch/lbs for silicon gaskets.

Next step was to bull off the plugs off the cold air intakes on the sump, and the intakes on the cylinders and install the intake tubes. This was a lot of fun, and I was quiet surprised just how well the tubes lined up – perfectly in fact – no wrestling or fiddling required. Used gasket paste on all gaskets, then torqued them onto the cylinders at 80 inch/pounds. Also used the shiny new hoses and clamps to fit the intakes to the sump. Went off quite easily and looks nice.

I then installed the oil drain tubes, which was a mistake since that prevents the baffles from going on, so I’ll come back to describing that. I had to take them off to do the baffles. With the baffles “dryish”, I installed them onto the cylinders. Gary had gone at this stage but had left a small hook tool for grabbing the interconnecting hook and feeding it through the retainer on the top between the cylinders Took a bit of time to work it out, but when done they fitted on quite easily. Messed a bit of the RTV on the fins, but cleaned that up.

Then it was time to install the cylinder head oil drain tubes. I had the original ones from the engine, and even the hoses looked in good nick, so I simply washed them in fuel, scuffed the tubes clean, and installed them. Each one can only go on a certain cylinder, so it was easy to work out what goes where, and they all lined up perfectly. Paused briefly when I noticed paint on the aluminum fittings on the cylinders since I know you want a clean face when connecting flared tubes to fittings, but I’ll check with Gary on that later. After a while I had them all connected up. I even remembered to use white pipe thread sealant on the threads before tightening up.

I then installed the Raven Vac Pad Adaptor for the inverted oil kit onto the accessory case along with a gasket, and then installed the Skytec starter on the engine. This was easy enough, most of the problem was hunting through the box of cad plated nuts and bolts to find the right hardware. That was pretty much all I achieved today. Gary mentioned he now wants to run the engine up after all before I take it home to the aiframe, so that’s very exciting! Apparently it will take a whole weekend to connect it up to the test rig, but I’ll get to see how the engine performs with standard exhaust tubes, and then with the 4-into-1, so that will be very interesting indeed.

Took a few pictures, and headed home.

Time taken 7.5 hours. Total time: 1172 hours.