GTV 116 supercharged NORD

[Midda Samid]

not sure anyone is interested but my wife is sick of hearing about it..

have the new pulley now.. 170mm.. pic attached.. will push the drive up to about 2.4:1 and hopefully the boost above 8psi.. we'll see this weekend.. belt is coming friday. I can't fit a larger pulley than this as it will contact the chassis near the jack point at the front of the engine bay. The drive ratio will see the charger running at the limit of it's efficiency at max engine rpm anyway..

Airbox is almost finished with cold air intake to radiator facia as per pic. I still need to make a duct from beside the highbeam to the mouth of the cold air to make sure it gets air.. new fans are mounted on the alum radiator, wired up and controlled by the computer..

Low comp engine not started yet.. wanted to sort the boost levels before i started another project.. will start stripping the old engine next week.. balancing of the rotating stock will happen soon after that and then just rings and bearings rebuild with TS rods under Nord pistons.. all else will stay standard.

[Mike]

Boost!!!   Must have boost!!!

Mmmmm....I spy carbon.

[Storm_X]

What type of radiator is that ?

[Midda Samid]

Ok.. finally got the pulley on and a belt that fits.. it seems the design is in between belt sizes.. I am running a 5pk1370, but really need a 5pk1360.. no one makes this one..

Had some electrical gremlins that has delayed my test drive, issues with idle and idle air stepper aswell.. With those resolved I got it started last weekend to find that increasing the drive from 1.8:1 up to 2.4:1 increased it's decibel output from "pretty reasonable" to "downright offensive".. infact, it was so loud I decided I couldn't even test run it to find out what boost levels my new pulley was getting me... So, with disappointment, I almost conceded that a streetable supercharged Alfetta was infact a dream that I couldn't make come true.. But hey, the German giant Mercedes can make a streetable car, surely I can too on my meagre budget.

I visited a Merc wreckers on friday, and grabbed the intake resonator from the M271 supercharged 1.8L engine. It's a little plastic box that fits inline between the aircleaner and the charger(item 100 in the attached pic).. It has a series of internal chambers and perforations that assists to make the Mercedes a streetable car(they have 2 output resonators aswell).. I figured it was worth a shot. So, fitted yesterday, and still using the megaphone style pod filter as seen in previous photo's, has unbelievably brought the charger noise to an acceptable level.. Test drove it tonight. It still has some noise about it, but I am suspect as to the condition of the charger(to be confirmed on inspection by a pro) and will further reduce noise with an airbox and cold air intake which still fits with the resonator in place... Dream is back on track.

The thing is pinging it's little head off now though.. I have a theory that the pulley guys disassembled my crank pulley and striker plate for the crank position sensor (when they were cutting the new charger drive pulley..) and have reassembled it out of phase and thrown my timing off. This to be proven with a timing light (however not at 9pm at night since my sleeping kids might have a problem with an idling supercharged Alfetta in the garage).. It might explain my almost hydraulic lock when starting too.. almost like an engine with a blown head gasket that has water in the cylinder.. But it doesn't. The car ran fine before the pulley guys did their thing.. it's the only thing that has changed. The engine is tuned for 5psi, so it should be fine.

But, all said and done, I have boost.. it's hard to gauge just how much, but it's more than 7psi which is reassuring.. the pinging is so bad that I dare not risk a WOT to check total boost.. The car is running super hot as well even with the feathered throttle that I drove it with(so not a boost thing).. ambient air is prob around 12-13deg, so poorly set timing would add to this also..

What type of radiator is that ?

StormX, I had it built by a rad place in dandenong.. it was cheaper to have the original one copied in alum than it was to have the alfa one refurbished at the time as I lumped it in with an intercooler build(the one that Mike has just decommissioned on the twincharge).. So, to answer you, it is a copy of the original.. In hindsight, I should have spent the extra and got the original one rebuilt as it is better for heat transfer, but that said, it is very easy to make changes to things like fan location and orientation of the inlet and outlet spouts on the alum one..(i just pay someone to do it.. haha) .. my last build ran an elec water pump, so the outlet spout of the rad pointed up toward the battery mount where I had the pump located. I had a gutted waterpump housing welded up to get the water into the block.

And Mike, you might have hit the nail on the head with your guesstimate of around 7psi on my setup.. damnyou.. haha.. I hate it when other people are right.. although, I have my hopes in a WOT and cracking the 8psi minimum i set myself to leave the setup alone.. if I don't get it, I am back to the drawing board with a bigger charger.. i might lie to you to avoid this.. haha

Oh, and I have a pretty Autometer boost/vac gauge mounted in the dash cutout where the choke and throttle lever usually go.. the 2 1/16" gauge jams straight in there.. from where I sit I get a clear view between the hoop and the top right spoke of the steering wheel.. much easier to read than the Wolf screen when driving. Just need the Tacho modified to accept the Wolf output and I will have all the info I need..

long post.. sorry.. today is a good day.. the car works. back on track.

[Midda Samid]

Oh, and Mike, the carbon you spy is just 200gsm woven fibreglass fabric.. not too bad to work with.. a little tough to make it turn corners, but looks ok.. It was my first attempt at fibreglassing anything, so can't complain.. the black dye covers any air bubbles that got trapped at the sharp turns.

The airbox is moulded on an X300 jaguar XJR airbox with the top cut off it.. It's a pretty tight spot where I am trying to fit it.. The filter element is the main reason I chose it (high flow for the supercharged 4.0L jag) and also the angle spout on the base that runs down the splash guard to where the A-pillar and the shocker tower meet. I can fit the inlet resonator behind the exhaust mani against the firewall and still get plumbing to the airbox.. Still arranging the fibreglass patching for the base of the box before I can use it..

[Midda Samid]

Here's a pic of the boost/vac gauge.. the only mod was to drill 2 holes in the mounting plate for the throttle and choke lever to receive the gauge threads.. the gauge comes with knurled nuts.. lighting came straight off the spare spade terminal on fuse9? i think.. which ever fuse the dash lights work off.

and a pic of the resonator with the pod filter set up for the test drive. (don't mind the hair pin holding the hazard button in - actually, does anyone know if there is an aftermarket replacement hazard switch that can be used inplace of my hair pin or are new switches available anywhere?)

[Midda Samid]

OK, sorted the pinging issue.. The crank angle sensor striker plate had been reassembled 36 degrees advanced.. so at idle I was running 48degrees advanced and at higher rpm, pushing out to some 65+degrees.. thanks for that pulley guys.. To be honest, I am surprised it ran at all.. I won't bag them too much, I should have marked the pulley to striker relationship before I gave it to them.. I asked them not to disassemble, but knew they would. Rookie mistake.

So, surprisngly it only took me 3hrs to get the front pulley off and sorted and back on again... I can fit a rattle gun between the bottom of the radiator facia and the underside of the intercooler from the under bumper vents.. I had to undo the drvers side engine mount and jack the engine to remove the pulley, so radiator out, belts off, intercooler piping off.. then all back on.. 3hrs will do..

Drove it today.. will disappointingly admit that max boost pressure was only 6.8psi(don't tell Mike, I can already hear him laughing).. the car really steams, but my target was a minimum 8psi to keep the setup and I originally wanted 10psi, so it's a far cry from the original plans.. Since I am running the charger pretty much flat out and the chassis won't allow a larger pulley anyway, then I suppose I have to admit defeat on this one and up the charger size.. ouch.. I chalk this one up to a practise run..

I won't be building any engines until I actually require one.. 6.8psi certainly doesn't require a lower comp ratio.. It's fun though, so will sort the exhaust and complete the build with airbox and cold air, and either drive it until I break it or until I find the next charger... I have tried breaking this engine before and failed.. I expect the charger will come first.

This isn't over.

[Duk]

Drove it today.. will disappointingly admit that max boost pressure was only 6.8psi(don't tell Mike, I can already hear him laughing).. the car really steams, but my target was a minimum 8psi to keep the setup and I originally wanted 10psi, so it's a far cry from the original plans.. Since I am running the charger pretty much flat out and the chassis won't allow a larger pulley anyway, then I suppose I have to admit defeat on this one and up the charger size.. ouch.. I chalk this one up to a practise run..

I won't be building any engines until I actually require one.. 6.8psi certainly doesn't require a lower comp ratio.. It's fun though, so will sort the exhaust and complete the build with airbox and cold air, and either drive it until I break it or until I find the next charger... I have tried breaking this engine before and failed.. I expect the charger will come first.

This isn't over.

Have you checked for flow restrictions before the supercharger's inlet? Attach a water manometer to the SC's inlet and go for a full throttle squirt, that will show up any pre-supercharger air flow restrictions that will hurt power.
Similar for boost pressure testing. Have you tested the boost pressure at the SC's discharge port?

[Midda Samid]

Thanks Duk, I haven't check charger discharge pressure yet.. it's on my list of checks to make sure the cooler isn't too small or restrictive.. It is a cheap cooler, so I expect some restriction.. it does well with the charge temperature(max 30deg in about 17 ambient), so it has to be failing somewhere for the cost.

Can you explain the inlet restriction test for me.. I don't understand.. Is it a calculation of expected airflow versus actual.. manometer tests pressure, so I suspect I will be testing vacuum? how does vacuum indicate restrictions? At best I could calculate an estimated airflow using the inlet area and estimated fluid properties(doesn't sound very decisive).. I am new to problem solving though, so will take any advice I can get.

If I was seeing inlet restrictions I would think boost pressure would drop as requirement for air increased(high rpm).. I would expect the same if I was seeing discharge restrictions also.. as air flow increases, system inefficiencies will show themselves almost exponentially..

I have since found a larger charger that I am close to buying.. just waiting on a freight cost and I should be the proud owner of an m62 in a postpack.. I am hoping I can use most of my fabricated steelwork for the mounting as there has been considerable hours thrown at it.. it will all depend on it's height and setback from the pulley..

[Duk]

Can you explain the inlet restriction test for me.. I don't understand.. Is it a calculation of expected airflow versus actual.. manometer tests pressure, so I suspect I will be testing vacuum? how does vacuum indicate restrictions? At best I could calculate an estimated airflow using the inlet area and estimated fluid properties(doesn't sound very decisive).. I am new to problem solving though, so will take any advice I can get.

Yeah, you're reading lots too much into it  . The water manometer at the SC's inlet is just a sensitive pressure gauge. If the SC can move more air than what atmospheric pressure can fill up, the will be a pressure drop below atmospheric pressure (a 'vacuum').
As an example, the my factory supercharged Toyota MR2 had a pre SC throttle body so small, that at full throttle at about 5500rpm (from memory) it would pull 4"Hg (mercury) vacuum between the TB and the SC. That's 2 psi! That meant the SC wasn't getting filled with 14.7psi of atmospheric pressure, but only 12.7psi.

But anyway:

If I was seeing inlet restrictions I would think boost pressure would drop as requirement for air increased(high rpm).. I would expect the same if I was seeing discharge restrictions also.. as air flow increases, system inefficiencies will show themselves almost exponentially.

Good point.

[Midda Samid]

nice.. found an article on autospeed relating to inlet restrictions today.. used the same method.

[Midda Samid]

I am watching a supercharged 2.5v6 thread on alfabb where both Greg Gordon and the car's owner think the boost levels should be increasing with a positive displacement charger with engine RPM due to volumetric efficiency improving with rpm??? 

Would be interested in hearing some ideas or thoughts on this..

I guess i would agree if the supercharger rpm starts very low when the rotor clearances are allowing air to 'slip' by, but in a typical supercharger install where the charger is sized for the engine to minimise parasitic loss and maximise adiabatic efficiency, i'd expect a pretty flat volumetric efficiency curve.. ie, a small charger working flat out will have a better (and more linear) volumetric curve than an oversized charger running very low rpm for same volumetric output per engine rpm??

can anyone confirm or argue this?? Duk, Mike, i am looking to you..

I suppose I am wondering, (if this is the case), then what sort of boost shift would you expect to see? it'd be marginal at best, surely?..

[Duk]

I am watching a supercharged 2.5v6 thread on alfabb where both Greg Gordon and the car's owner think the boost levels should be increasing with a positive displacement charger with engine RPM due to volumetric efficiency improving with rpm??? 

Would be interested in hearing some ideas or thoughts on this..

I guess i would agree if the supercharger rpm starts very low when the rotor clearances are allowing air to 'slip' by, but in a typical supercharger install where the charger is sized for the engine to minimise parasitic loss and maximise adiabatic efficiency, i'd expect a pretty flat volumetric efficiency curve.. ie, a small charger working flat out will have a better (and more linear) volumetric curve than an oversized charger running very low rpm for same volumetric output per engine rpm??

can anyone confirm or argue this?? Duk, Mike, i am looking to you..

I suppose I am wondering, (if this is the case), then what sort of boost shift would you expect to see? it'd be marginal at best, surely?..

I can only comment on what I read in Greg's book, which is the same information. It makes sense, too.

If you look at the Toyota 4AGZE (1.6 litre, twin cam, 16 valve supercharged) engine, they used an old straight 2 lobe per rotor supercharger that displaced 1.2 litres/revolution. The best factory effort was 120KW.
If you then look at the supercharged Mini's, same (basic) set up, capacity, head design and number of valves with nothing special about the motor (no variable as far as I know), but having to meet tighter emissions, 120KW. The Mini used the Eaton M45, which moves 0.738 litres/revolution.

I can't comment on the shape of each engines torque curve compared to each other, but I'd bet the Mini has better fuel economy.

Supercharger compressor maps really do tell most of the story.

[Midda Samid]

Not sure I understand the argument? if infact there is one??

I would imagine the Mini 3 lobe design is more efficient in a number of ways.. The fact that they can drive it at twice the speed to get the same volumetric flow rate is a good indicator of this.. the MR2 and mini setups are not comparable for this discussion. does the MR2 see an increase in boost pressures through the rev range? or the mini for that matter?

My question was more related to a positive displacement charger and the boost figures observed and whether they might increase wth engine RPM due to volumetric efficiency improving.

Surely, if a charger is seeing poor VE, it could only be due to basic design flaws like clearances between rotors and "blow by" of the fluid as it is drawn into the charger. If infact the clearances allow blow by, it will be an amount that I would expect would not change with each revoltuion regardless of how hard it is turning. 750cc's per rev and maybe lose 20cc's through clearances.. at 5000rpm, it will lose the same 20cc's each rev through the same clearances as it would at 13000rpm.. wouldn't it? so volumetric efficiency unless I understand the term wrong, is not changing.

Adiabatic efficiency is another story.. and generally shown on efficiency maps.. VE is not indicated on efficiency maps.. boost pressure, airflow, charger rpm and efficiency shading which I understood to be adiabatic.. infact, the relationship between airflow and charger rpm is amlost linear with outlet boost pressure

With an increase in inlet temps due to high boost pressures, you might see an increase in boost pressure as the pumped air increases in temp after the inlet of the charger. the charger draws the same 750cc's of ambient air and then heats it and shoves it into the inlet tract.. it expands, pressures increase.. this has nothing to do with volumetric efficiencies however... prob has more to do with heat soak of the inlet tract and charger body if t even happens...

I guess Greg G can't be wrong? I would be interested to learn more about it though.. obviously.

[Midda Samid]

Found an interesting read in Pat Ganahl, a complete guide to street supercharging..

page 37 has some info on the different thoughts and opinions around blower VE. It's on googlebooks..

I was given an equation to calculate boost pressure on a given engine with a known charger capacity and drive ratio. With my setup it, the calc's came to 12.2psi.. I am seeing 6.8psi.. vastly dfferent.. would be interested if anyone has supercharged anything if they could plug in their figures and see if they are close to the calculated answer..

(charger displacement/(engine displacement x 0.5))x(ratio x 14.7)-14.7 = boost

for me,

(750/(1962x0.5))x(2.4x14.7)-14.7=12.27psi

if I fudge the numbers a bit and shift the VE of the engine to 80%, it increases the boost pressure(obviously).. if I shift the VE of the charger to around 80%, I can get the numbers down near the boost levels I am seeing.. realistically, my charger would have to be shot to be seeing such low VE at the rpm I am running it.. clearances would have to be huge which would either mean that my rotors have shrunk(unlikely) or bearings are shot which would show contact marks on the rotors from either the housing or the other rotor.. my rotors look fine..

for my previous setup with the smaller drive ratio,

(750/(1962x0.5))x(1.8x14.7)-14.7=5.53psi, again, a far cry from the 2.3ish I was seeing..

anyway.. food for thought.