http://ackthud.com/shawnfogg/

Look down to the engine section

I find some faults with the way he calculated the VE changes with rpm but it shows the general trends as whatever the VE is a torque peak [by definition max VE], there is a slow progressive decline to the HP peak as the atmospheric pressure doesn't have as much time to fill the cylinder!

Many people think the piston moving down sucks in the air, not true, the air pressure blows the air into the cylinder. Since the intake valve is open 248 degrees out of 360 every other rotation [cycle] it is open 34.4% of the time. The cam to valve lift [0 to 0.390"] makes a curve [graph] as the restriction [valve is lifted off the seat]. A the mid point [124 degrees] it starts to close.

As the valve opens the CFM increases then decreases as it closes ....you must measure each of 700 positions in 0.001" increments to determine the actual shape of the curve. Thats what you do on a flow bench [maybe only make 10 -20 measurements and extrapolate the curve will be good enough].

http://www.airflowresearch.com...t.htm

4 valve per cylinder engine need less valve lift because the 2 valves area [1.5 " diameter= 1.767 sq' x 2 or 3.534 in total] vs 3.14159 for a single 2.000" [or smaller] found in a Chevy 350 V8.

http://www.araoengineering.com/Chevy/chevybb.htm

Most engineers use 0.400 lift as the average comparison point anyway so gigantic peak lifts only mean gigantic strong springs which limit rpm due to valve float!

Too much lift with large dual intake valves is BAD at low rpms just like too much cam duration is BAD.......the tricky part is getting a good idle, good cruise torque [enough to move the car at the least fuel consumption [rpm] possible], while making high peak torque and not allow the efficiency to drop to fast so the HP numbers are good [for marketing].

750>2000>4000>6000 and a redline of 6900 or 7300 is quite a wide range.

"Many people think the piston moving down sucks in the air, not true, the air pressure blows the air into the cylinder. Since the intake valve is open 248 degrees out of 360 every other rotation [cycle] it is open 34.4% of the time. The cam to valve lift [0 to 0.390"] makes a curve [graph] as the restriction [valve is lifted off the seat]. A the mid point [124 degrees] it starts to close."

so in essence the draw into the cylander is actualy like a pressure equalization , makes sense since diesels dont devlop much of a vaccum as there is no butterfly or anything restricting the air into the engine . you mentioned cam timing there , so if you slamed the valve shut too early you would actualy drop the compression ratio, since the pressure equalztion wouldnt have enough time to work properly right?

"4 valve per cylinder engine need less valve lift because the 2 valves area [1.5 " diameter= 1.767 sq' x 2 or 3.534 in total] vs 3.14159 for a single 2.000" [or smaller] found in a Chevy 350 V8."

ive heard 2.02 valves are actually a little big on a small block and cuases idleing problems (low "vaccum" or something), now the q has a ammount close to that yet has 1.2 liters less is this why the Q45 had variable valetimeing early on ? or is the cam timeing adavanced far campared to a normal cam timeing? or does the less lift cure that totaly?

just thinkin

Having no [well only 8 degrees] of overlap at idle until the rpms rise enough for the oil pressure to advance the input cam to the 20 deg BTDC position helps the vaccum tremendously but it is still only around 18-19 " HG......as the 2 -1.5" intake valves are big for a 274 ci engine.

You set the runner input diameter [at plenum] to taper down to the valve diameter at a ratio between 0.70 and 0.80 so for a 562 cc cylinder 2" down to 2 -1.5" valves which because of the stem and tapered shape and valve seat obstruction act like 2-1.1" areas.

http://staffi.lboro.ac.uk/~elvpc/papers ... frdsmb.htm

You are correct! static compression ratio means nothing without knowing the total input flow as a 4valve engine out flows a 2 valve engine in every case so a 10:1 is meaningless. What you need to know the the peak/average BMEP for each rpm.

The newer FULL VVT/ Vlift cam systems use this to have a 11:1 but lower the real CR when it is not need or wanted at cruise to replace the EGR.....they allow more exhaust [spent gases high in CO2] to remain thus diluting the input charge [if 25% exhaust is still in the cylinder only 75% new air can flow in [11 x 0.75=8.25 running CR].The torque peak is most sensitive to CR so they can dip before it and just after, progressively increase the percentage [real CR] as the valve runner friction increases towards and above the HP peak.

I sometimes wonder about all the misinfo about CR it makes the Real engineers run from such user forms because the members and the engineers have nothing in common

Most engine design is done on computers in Math simulations.http://www.simcar.com/literatu...e.htm

FYI: A wierd 4.5 V8 FWD that hasn't made it here yet [thank goodness] with SMALLER valves---Two intake valves of 35.5-mm (1.40-in) diameter and two exhaust valves of 30.5-mm (1.20-in) produces 10% less torque and even less HP. http://www.sae.org/automag/globalview_03-00/04.htm

http://www.idavette.net/hib/02ls6/listpages.htm

read them all especially the 4th down " PUPS OUT " see that removing the precats only gained 5 HP out of 385/405 HP with fuel recalibration.Induction and Calibration Upgrades next shows how the factory fixed the airbox and MAF restriction.LS6 Evolution: Bigger Cam–Again

Shows how they made minute changes [in lift] and added sodium cooled exhaust valves to the new Corvette....Sound farmiliar!

getting 20 HP took a lot of work....thats 1.17 per cubic inch almost 72 per liter maybe they get close next year or the next to thecurrent Q's 75.6 per liter.

A vette power Q is getting more and more attractive: 400 lb/ft with a better AT would knock 1.5 seconds off the quarter.....13.6 @ 103-104 mph????????

it appers there opeing the cam sooner trying to get pressure equalization beatter by opeing the valve sooner and closeing at the same time as the old unit , are they dealing with too small a intake valve i wonder?

wonder if the head will try to wear out the valve seats , they didnt mention anything about changeing them in any way even thogh the springs are tighter and the closeing load is more , ii suppose it will be ok prorbaly only cut down a few thousad off the engines life but just makes me think

looks like GM is beginning to listen to there customers , makes me wonder if the "ring flutter" exists in the 99 chevy i have as a shop truck , thing uses all kinda oil with 17,000 on the clock , seems to be the same "light load" high rpm that the vette was dealing with depending on what rpm range there talking about coarse its a older small block design not the new 5.3

On the other hand dads 5.3 does have piston slap at cold start up and it is a corvette related engine , looks like some odd ball pattern stuff in the advanced "vette" engines

anyway good reading there

http://www.engr.colostate.edu/~allan/engines.html

"abnormal combustion is particularly common in force induction engines, where exhaust temperature can exceed 1100°C! WHAT CHANCE has a piston got under these conditions, given that aluminium melts at 660°C? 99% of production cars keep exhaust temperature below 850°C by fuel-dumping, and hold crown temperature below 550°C by conduction to the underside and skirt of the piston, which is constantly being quenched by engine oil. Most of the heat is transferred to the cylinder wall. ........................."http://www.aquamist.co.uk/dc/dc.htmlhtt ... ha...y.htm

http://www.spdusa.com/serv02.htmhttp:// ... pensi1.htm

Lots of suspension info on upgrading an Imprezza/WRX sure they only weigh 2800 pounds but the discussion of how cars are detuned for extra safe handling in US is all good stuff.

The rear sway bar 15>18>20 mm upgrade and effects, the discussion on springs and how the rebound is controlled

On to something else:"Alternators are about a maximum of 60-65% efficient, typically, so if you add a new load of 200W (say 15 A) to the electrical circuit you will lose about 1 hp at the flywheel, on average.

Larger current capacity alternators are designed by the same people working to the same constraints, so I doubt that they would be much more efficient. Incidentally when an alternator is rated at 110 amps, that does not mean that you will get 110 amps at 14.2V out of it, it means that if it is going round fast enough you will get 110 amps. Figure on 6000 rpm plus for an automotive alternator to reach its rated output (eyeballed from the graph). Incidentally the efficiency drops with speed - at 15000 rpm the efficiency at full current has dropped to a miserable 38%. Alternators also have a maximum speed, so you can't just up the pulley ratio to improve the performance."""

From one question of this auto engineers forum:http://www.eng-tips.com/gthreadminder.cfm/lev2/6

http://radiatorreporter.com/electrol.html

http://www.tarorigin.com/art/Dgilman/

Data is stored in the seat belt/airbag system: vehicle speed, engine rpm [gear selection], throttle position, brake switch, seat belts of all passengers-- GOING BACK 5 seconds before the event.

The SDM is designed so that 150 msec after the deployment algorithm has enabled, all the data stored in memory is permanently written to the EEPROM. Once a deployment record is written, it cannot be erased, cleared, or altered by service or crash investigation personnel.

This near-deployment event is cleared from memory after 250 ignition cycles, or about 60 days on average.

The available data sources are immense since about 18,000 tow-away crashes occur daily.

http://www.tarorigin.com/art/Bschmidt/h ... arness.htm

http://dept.physics.upenn.edu/....html

investigators and innsureance companys will love that , no more estimateing speed by skidmarks , now they can say "yup he was runing 87 mph with 100% thorottle , not only does his car blow but he was going 32mph over the limit"

How does a turbo work.Can I put a turbo on my 93 J30?

where do we start , turbos and how they work...

okay , you know that air that comes out of the engine right?

ok lets contain that air and run it up against a fan , ok now we have made the fan begin to spin lets place another fan on the other side of the fan thats spinning but keep the exaust/used seperate.

so now we have a fan that is rotateing generateing a nice breeze (lets say 7 psi) ok we'll contain that breeze and shoot it over to your intake manifold where we can cram that air into the cylanders (since more oxygen makes more power and more air brings the compression up) . good now its time for the new bigger injectors you installed at the same time we put the turbos on your j to fire some fuel into the cylander . the rest is normal otto cycle stuff .

now to turbochagre the J , ill make it easy for you , send me your J and 25,000 dollars , it may come back looking like a 300zxtt and have difftrent vin numbers but hey its turbocharged . actualy a few people have swapped in the whole drivetrain out of a 300zxtt into there J , this would eb the best soulution in my opinoin to your turbo dilema.

It would be worth our wait until our J30 gurus chime in.

In the meantime let me point out that the J Chassis and powertrain have a lot in common with the 300ZX, which as you know came out as a twin turbo.

So it shouldn'ty be a difficult to turbo charge as many other cars.

Fred...

hidden inside the "more interesting reads" i seriously dout the J- 30 gurus would think there are questions posed on J30s in this thread

otherwise i would have shut my mouth , really didnt feel like chewing him out cuz he didnt make a new thread . i know a few things about turbos and i thought id help out , sorry

I found your posts very informative Stone.

OK I got the message.