Aaron Rouse

Jim at that boost level you could get away with no intercooler at all. I know of a 86.5 928 that has a single T04E turbo on it, 4.5L bone stock motor, TEC II, bigger injectors and I think that is it. Car is daily driven and only problem he has is the TEC gets too hot, but those TEC II's are known to do that. He runs no intercooler and about the boost levels you just mentioned.

If I were to ever regain interest in my twin turbo setup, I probably would initially try no IC(which means I got everything to bolt up) because that was always my big debate as well. BTW, same person with the single used to have a twin setup and ran a IC in front of the radiator, took a custom radiator that was not as tall and a custom AC condensor. I believe he measured no real temp drops by adding it to that setup, but not 100% on that after so much time has passed.

GoRideSno

For the record.

I finally drove the car for about 30 min today.

I am pretty sure now that I am making 4 psi.
Which means ((14.7+4)/14.7)x316=401 it should be making around 400 hp. I am using the smaller crank pulley.

The reason for my making less boost than calculated could be that I have removed the teflon from the rotors of the blower because it was flaking. Two rebuilders have told me it dosen't do much and they remove it if it flaking.

The car is definately much faster.

For the record there is no boost unless the engine is under load. Boost varies with engine load and throttle position.

I am getting plenty of fuel acording to the ARM1.

The engine is getting really hot though.

Andy K

TAREK

Aaron,

Not to distract from the subject of this thread, but how can an 86.5 be bone stock with a 4.7 liter engine? Please correct me, but I thought all 86.5 models came with the 5.0 liter 32 v (Pre-S4) engine. Was the 4.7 liter installed for making room for the turbo?

Andy,

Do you feel that removing that flaking teflon contributed to increased exit temperatures effectively turning the performance of the MP112 to that of an M112?

GoRideSno

Tarek,
You pretty much hit the nail on the head.

Removing the teflon will probably leave a wider space between the rotor and the casing too. This will let more air slip by creating less boost.

Regardless it still hauls AR$$.

It is comforting though to see the other MP112 with teflon sitting here on my kitchen floor next to the Ford lightning Intercooler. All just waiting to be attached to the redesigned manifold.

Andy K

Z

You're not taking into account the heat thats being created reducing the density of the air. That will reduce the power from that mentioned above. It would be interesting to see a dyno chart, more to see what the actual curves look like than the actual power numbers made.

atb

Lagavulin wrote:

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Both Corky and Graham Bell state the each point of compression ratio is worth 4-5% horsepower </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">There was an article in one of the hot rod magazines not too long ago where they took a N/A Mopar 440, and by stacking head gaskets (and using adjustable push rods) were able to vary the compression ratio. I think they took it from 8:1 to 12:1. The engine was not optimized for any particular C/R, it was just run on the dyno, heads pulled, gasket added, bolted down, and run again.

They found a 3% gain per C/R point.

Tony

Andy, the engine temp may be due to the fact that the roots does take a bit more OOOOMPF to power, thus loading up the engine some more?

I think when you get the intercooler set up it will be better.

In the meantime go through your cooling system and give it a one over...fans..tsat..etc.
perhaps a flush?

Also...doesnt Saab curently run a Turbo engine with variable compression? the whole head is on a cam of sorts and gan be moved...i have know idea how they do it, but im pretty sure it was SAAB doing the work with the idea
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

John..

Guys, forget about sleeving and go in like I did and plate the bores with Nikasil.

Sleeving is fine for a low use race motor, but on the street for daily driving the Nikasil should prove more reliable.

Why:

Tighter tolerances and better heat transfer.

BC

I disagree John. Sleeving is no longer a race only deal. It can be done with longevity in mind, and the bores that I have seen done are far more than you could achieve safely with simple rebore and plating. Also, when you factor in the idea of thermal technology, and the fact that at one point, Engine designers were trying CERAMIC engine blocks, then the whole heat transfer ideal changes. If a Sleeved block will transfer LESS heat into the coolant, and MORE out of the engine into the exhaust, then I have no problem with that. There are coatings that are supposed to be put on to the combustion are on the head, as well as the top of the piston, so that MORE heat exits the chamber than is absorbed by the walls and head and piston. Thats what you want for your turbo, if we are to believe that the turbos are driven by the heat engery crested by combustion.

Sleeving is the way to a 106mm bore, with whatever stroke strikes your fancy. 6.5 or so of literage, with some 10-13 pounds of boost. Thats power.

Jim Nowak

John,

Did you ever determine the cause of the 10% leak down when you tested your new motor?

LT Texan

John, I know it's been asked before...but what abou the high sulfer content in US gas and the pitting it causes in nikasil lined bores?

Lagavulin

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">by Jim V:
Brendan, I don't think any of them would make boost no-load even a 4K RPM.. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">This is not true. The roots and screw type blowers are referred to as 'fixed displacement' compressors, meaning that for one revolution of the compressor, it will move a given amount of air, load or no load, unlike the centrifugal.

It is why the roots and screw makes so much boost down low, and why one can have full boost at only 1,200 RPM with these types of blowers.

However, it is true too that the faster it spins the more 'efficient' it gets as there is less time for the charge to leak past the rotors.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">by Aaron R:
BTW, same person with the single used to have a twin setup and ran a IC in front of the radiator, took a custom radiator that was not as tall and a custom AC condensor. I believe he measured no real temp drops by adding it to that setup, but not 100% on that after so much time has passed.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Evidently something was wrong here as one can expect over 80% efficiency with a properly set up intercooler. What that means is that at least 80% of the heat added to the ambient temperature by the blower will be removed by the intercooler, resulting in a lesser chance of detonation, a denser charge, subsequently more horsepower, and helps build strong bodies 12 ways.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">By GoRideSno:
For the record there is no boost unless the engine is under load. Boost varies with engine load and throttle position.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">That's very interesting as it's inconsistent with how a roots typically operates. Is the unit in a known good state of health?

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">By GoRideSno:
The engine is getting really hot though.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">What do you mean by this? What is 'hot', exactly?

Does it run hotter than normal out on the highway at highway speeds? Or, does it run hotter when just running around town stuck in traffic?

If it's running hotter around town, have you verified that the fans are kicking in when they are supposed to?

I hope you can get this sorted out...

ViribusUnits

Lagavulin you are correct that a postitive dispacement, and a centrifical force super charger will make the same amount of boost at any rpm, load or not.

However, a properly designed system eighter has a blow off valve, or a TB infrount of the charger. When your have little load, the blow off vlave blows off all the excessive boost. You see, with no load, the required mannafold pressure on the engine is a pretty strong vacume, to reach any rpm. Result, no boost on the mannafold. In the other situation, the TB is placed infrount of the charger. At minimal throtal, the vacume is close to 14 psi. Thats a vacume of 14 psi, or .6 psia. The turbo or supercharger can be mathamaticly modeled as just multiplying the pressure of the incomeing air by some number to get the pressure of the out going air. Very little psia, multiplyed by any number, equals very psia. Again, no boost.

However, when your go to WOT, with a load on the engine, the engine goes to full boost that the unit can supply. The blow off valve closes, the TB opens, and you get to see what happens.

Under a WOT, the centrifical starts out with very little boost, and steadly builds at a geometric rate untill reaching WOT, and full booste. I'm guessing you could put some sort of a tough throtal valve downs tream of the blower, and use it as a regulater, allowing you to reach full boost at some much lower rpm, and then use the regulater to keep it with in the allowable limits. I've never seen, or even heard of, a unit created as such, but my background suggests it's possible. Maybe I'll be the first to do it. :-)

A turbo builds similer to a centrifical unit, but can be controled with a waste gate. This allows you to put a small turbo on, haveit spin up to the boost that you want, at a low rpm, and then as the flow through the engine increases, the waste gate opens. The boost remains the same as the maximum allowable level.

A roots starts off at maximum allowable boost at idle, and stays that way, all the way up to the red line. The problem is that as it gets closer to red line, it's efficency falls, and the air stream gets hotter and hotter. Not so good.

I hope this helps. Please feel free to correct anything.

Lagavulin

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">By ViribusUnits:
I hope this helps.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Yes it does, thanks.

To be honest, I haven't researched how and when a blow-off valve should operate so I guess that's next on the list.

BC

The BOV and "wastegate" combination after a Centrifugal SC is what IH ave thought about for a while. The pumping loses might get in the wayof my ideals, but essentially, if you wanted boost down low, and then held until redline, then you would get a blower to boost to say 10psi by 3k, and then have it held there by a wastegate until 7k. The normal way, if I am correct, is to gear it to provide 13psi at 7k, and simply have the build up go naturally, i.e., not much boost at 2k. This would obviously be easiler on the drive train.