27 replies to this topic

[MatsNorway]

36lbs of boost! Google told me that was 16.3KG!

what's going on here??

[Ross Stonefeld]

Didn't CART engines make 40-44?

[Wuzak]

The Rolls Royce Merlin RM.17SM was tested in 1944 at 3150rpm (normal max was 3000) and 36psi boost using special fuel (PN160 fuel with extra TEL) and Anti Detonation Injection (water). It ran this way for 15 minutes (IIRC) in a sprint run, and made 2620hp (production Merlins at that time ranged from 1450hp-2000hp depending on mark and fuel being used).


36psi boost is equivalent to (roughly) 3.5bar MAP.

In 1987 the boost limit for F1 engines was set at 4bar. For 1988 that was reduced to 2.5 bar (IIRC). I am not sure if these are actual boost numbers (ie presssure above atmospheric) or absolute maniold pressures.

Edited by Wuzak, 23 September 2010 - 18:57.

[MatsNorway]

The Rolls Royce Merlin RM.17SM was tested in 1944 at 3150rpm (normal max was 3000) and 36psi boost using special fuel (PN160 fuel with extra TEL) and Anti Detonation Injection (water). It ran this way for 15 minutes (IIRC) in a sprint run, and made 2620hp (production Merlins at that time ranged from 1450hp-2000hp depending on mark and fuel being used).


36psi boost is equivalent to (roughly) 3.5bar MAP.

In 1987 the boost limit for F1 engines was set at 4bar. For 1988 that was reduced to 2.5 bar (IIRC). I am not sure if these are actual boost numbers (ie presssure above atmospheric) or absolute maniold pressures.

thanks. so no actual biggie then.

What does MAP mean?

[jimjimjeroo]

Manifold Absolute Pressure, pressure inside the inlet manifold (air intake)

[Greg Locock]

Manifold Absolute Pressure, pressure inside the inlet manifold (air intake)

No, manifold air pressure, measured relative to ambient. So full throttle is about -0.5 kPa, idle is at about -60 kPa.

[jimjimjeroo]

No, manifold air pressure, measured relative to ambient. So full throttle is about -0.5 kPa, idle is at about -60 kPa.

Sorry mate, but your are wrong...

http://en.wikipedia....wiki/MAP_sensor

Think you are thinking of MAF (mass airflow sensor)

http://en.wikipedia....ass_flow_sensor

[Greg Locock]

shrugs, I have worked as an OEM engine calibrator. Full throttle is near as dammit 0 kPA, whereas if it was absolute then it would be 100 kPa

[gruntguru]

Nothing here to argue about.

Like most things (particularly acronyms) I think it depends on the individual car maker. Certainly GM use MAP as an acronym for Manifold Absolute Pressure sensor. Either way, a MAP sensor is used to measure manifold pressure ranging from zero (abs) to 1.0 bar in NA applications and zero to > 1.0 bar in supercharged applications. In all cases the MAP sensor produces a signal for processing by the ECU which is usually an analog voltage or modulated frequency.

It is entirely up to the individual technician, technical writer (of workshop manuals) etc whether to convert this signal to units of vacuum (zero at atm and increasing as pressure falls), absolute pressure (zero at vacuum and increasing as pressure rises) or guage pressure (zero at atm and increasing as pressure rises, negative in the vacuum area). In the case of the engine-calibrator or diagnostic-technician, it mostly depends on what sort of guage he has in his tool kit.

[Wuzak]

What does MAP mean?

Manifold Absolute Pressure, pressure inside the inlet manifold (air intake)

No, manifold air pressure, measured relative to ambient. So full throttle is about -0.5 kPa, idle is at about -60 kPa.

I have always taken MAP to mean Manifold Absolute Pressure, mainly in reference to WW2 suprcharged aero engines. British manufacturers specified boost as a gauge pressure, so 36psi boost was usually specified as +36psi. US manufacturers used Manifold Absolute Pressure measured in inHg. From memory +36psi is equivalent to 110inHg MAP at sea level. In Germany the units were usually Ata, or Atmospheres Absolute.

[gruntguru]

I have always taken MAP to mean Manifold Absolute Pressure, mainly in reference to WW2 suprcharged aero engines. British manufacturers specified boost as a gauge pressure, so 36psi boost was usually specified as +36psi. US manufacturers used Manifold Absolute Pressure measured in inHg. From memory +36psi is equivalent to 110inHg MAP at sea level. In Germany the units were usually Ata, or Atmospheres Absolute.

Conversion of the many pressure units in use can be very confusing. I find a few simple rules of thumb make approximate mental conversions easy.
1 bar (1 atmosphere) = (approx):
15 psi
30" Hg
100 kPa
10 metres of water

So converting +36 psi to inHg goes something like this:

36 psi(g) = 72"Hg (g) or 102"Hg (abs) (approx)

A more precise answer is 103.216 (Using Online Conversion Tool)

[McGuire]

Didn't CART engines make 40-44?

CART's regs were stated in MAP, manifold absolute pressure, in units of inches mercury depression-- absolute pressure meaning referenced from zero as opposed to atmospheric pressure, which is around 30 inches Hg or 14.7 psi. One inch of mercury equals .49 psi. So 40 inches MAP is around 5 psi boost while 48 inches is approximately 9 psi. At one point the CART popoff valve calibration was shaved down to 34 inches, which, as you can see, is fairly close to normally aspirated.

I have always taken MAP to mean Manifold Absolute Pressure, mainly in reference to WW2 suprcharged aero engines. British manufacturers specified boost as a gauge pressure, so 36psi boost was usually specified as +36psi. US manufacturers used Manifold Absolute Pressure measured in inHg. From memory +36psi is equivalent to 110inHg MAP at sea level. In Germany the units were usually Ata, or Atmospheres Absolute.

You are correct. MAP stands for Manifold Absolute Pressure, and that holds as the prevailing standard across the auto industry today. For example, if you plug a scan tool or translator into any OBD II vehicle and thumb over to the MAP sensor screen, it will read 101 kPa at key on/engine off or at WOT. It's reading absolute pressure. You can select English units and it will convert to In/Hg but it's still absolute pressure, not manifold vacuum. Gauge pressure is known as MDP -- Manifold Differential Pressure.

Ford's typical MAP setup is rather different than most in that instead of a straight DC voltage varying in relation to pressure, the sensor outputs a square wave -- constant amplitude (5v) with varying frequency in relation to pressure, 80 Hz at 101.6 kPa to 159 Hz at 0 kPa. Conventional sensors typically pull a 5v high reference line up and down -- 4.84-4.88v where I live, which is about 600 feet above sea level. In most systems, the MAP sensor also doubles as the BARO sensor -- at power up the ECU takes a snapshot of the MAP value, which it then uses as its atmospheric/elevation factor for that drive cycle. So if you start at the base of the mountain and drive all the way up non-stop (or vice versa) she will be running pretty ragged by the time you get to the end of the trip.

[MatsNorway]

36psi boost is equivalent to (roughly) 3.5bar MAP.

Thats 2.5bars of boost then. im guessing its not with absolute pressure. therefore 4.5Bar with it. Engine tuners never state with the ambient pressure.

[McGuire]

This is a Global aka generic OBD II datastream as shown by a typical handheld scan tool. Ign on/engine off, the MAP value is 98 kPa... which to be honest is a little lower than I like to see but is probably normal for this particular vehicle, though it could mean sensor drift or a bit of ground float. At idle the value is in the 50 kPa range, as expected.

The scanner is an Actron Elite I received recently sent for evaluation. Pretty good tool IMO, though one wrinkle I personally don't care for is that in enhanced (non Global) mode it won't show native units, for example volts in the case of the MAP PID. (PID = Parameter ID.) Or maybe I haven't figured out how to access them yet. Every PID has a graphing feature though, which is nice. Plug: This scan tool appears to be a pretty good value, right in the middle between cheap scanners with limited functionality/updatability and the much pricier OE-supported devices. Actron is a division of SPX so the technical backup should be first-class.



Having a fairly accurate analog MAP sensor built right onto the engine can be a pretty handy tool. For example, you can take the MAP sensor output signal and an ignition parade, throw them up on a dual-trace scope and watch manifold pressure isolated one cylinder at a time...great for diagnosing internal engine issues and pesky vacuum leaks. One step beyond the good old vacuum gauge, an under-appreciated tool in its own right.

Back to boost...36 psi is a lot, but not a WHOLE lot anymore. This car runs 36 psi boost and drives on the street. Runs the quarter-mile in the 6's at over 200 mph; now officially the quickest street car in the USA. Owned, driven, and tuned by Larry Larson, very sharp guy. Just as a point of reference, the diesel racers are running over 170 psi boost.



More info on this scene here: http://www.hotrod.co...nals/index.html

[MatsNorway]

Back to boost...36 psi is a lot, but not a WHOLE lot anymore. This car runs 36 psi boost and drives on the street. Runs the quarter-mile in the 6's at over 200 mph; now officially the quickest street car in the USA. Owned, driven, and tuned by Larry Larson, very sharp guy. Just as a point of reference, the diesel racers are running over 170 psi boost.

3.5Bar is not a hole lot any more but 170 psi... thats more like it! How do they do that? serial turboing or whatever it was.

Im on a regular basis dreaming about a motor with turbo and supercharging. In serial for some massive boost.
could also be build more for response and still get the same figures as the one in first post. Engine control starts to get real important when you get those power figures that they have. (1100hp i believe it got)

[Wuzak]

Thats 2.5bars of boost then. im guessing its not with absolute pressure. therefore 4.5Bar with it. Engine tuners never state with the ambient pressure.

Yes, that is 2.5 bar gauge,, and 3.5 bar absolute.

Sometimes power outputs are corrected to standard atmospheric conditions (pressure, temperature and humidity)

The Merlin I mentioned above made more hp on the dyno than stated, but this was corrected for ambient conditions.

[gruntguru]

This is a Global aka generic OBD II datastream as shown by a typical handheld scan tool. Ign on/engine off, the MAP value is 98 kPa... which to be honest is a little lower than I like to see but is probably normal for this particular vehicle, though it could mean sensor drift or a bit of ground float.

Did you check the window? There may have been a bit of a blow outside.

[MatsNorway]

Yes, that is 2.5 bar gauge,, and 3.5 bar absolute.

no, no that atmosphere pressure does not count as boost. 3.5 gauge, 4.5 absolute.

[Wuzak]

Thats 2.5bars of boost then. im guessing its not with absolute pressure. therefore 4.5Bar with it. Engine tuners never state with the ambient pressure.

Yes, that is 2.5 bar gauge,, and 3.5 bar absolute.

Sometimes power outputs are corrected to standard atmospheric conditions (pressure, temperature and humidity)

The Merlin I mentioned above made more hp on the dyno than stated, but this was corrected for ambient conditions.

no, no that atmosphere pressure does not count as boost. 3.5 gauge, 4.5 absolute.

I don't know how you go from 2.5bar boost (2.5 bar gauge) to a total of 4.5 bar absolute.

+36psi boost is 2.48 bar boost (ie pressure above atmospheric, or gauge pressure).

Ambient pressure is around 1 bar. So with 2.48 bar of boost the Manifold Absolute Pressure is 3.48 bar approximately.

[MatsNorway]

I don't know how you go from 2.5bar boost (2.5 bar gauge) to a total of 4.5 bar absolute.

+36psi boost is 2.48 bar boost (ie pressure above atmospheric, or gauge pressure).

Ambient pressure is around 1 bar. So with 2.48 bar of boost the Manifold Absolute Pressure is 3.48 bar approximately.

Im saying that the Boost specified is 3.5Bar without the atmosphere pressure. The reasoning is that atmosphere pressure is not what most call boost.

ex. My NA engine "got" 1bar boost. (sounds wrong does it not?)

im pretty sure im right on this one because 3.5bar was what the pikes peak saab, Per Eklund used and he claimed to have 800hp at 4000m so to get 1100hp at (most likely) sea level this guy must most likely use the same level of boost. 3.5bar on the gauge.

http://www.youtube.c...feature=related

Edited by MatsNorway, 25 September 2010 - 14:29.

[carlt]

those wheels are sooo wide under stock arches - it looks like they are bolted to the diff flanges - excellent !

[Wuzak]

Im saying that the Boost specified is 3.5Bar without the atmosphere pressure. The reasoning is that atmosphere pressure is not what most call boost.

ex. My NA engine "got" 1bar boost. (sounds wrong does it not?)

im pretty sure im right on this one because 3.5bar was what the pikes peak saab, Per Eklund used and he claimed to have 800hp at 4000m so to get 1100hp at (most likely) sea level this guy must most likely use the same level of boost. 3.5bar on the gauge.

http://www.youtube.c...feature=related

The boost specified in your original post was 36psi, which is 2.5bar over and above the ambient conditions.

That is equivalent to 3.5bar absolute, or a 3.5:1 pressure ratio on the turbo.

At 4000m the ambient air pressure is about 60% of that at sea level. Thus if he was getting 3.5bar of boost his MAp was around 4.1bar, and his pressure ratio nearly 7, or twice what you need to get 36psi boost at sea level.

Not sure how you compare the car in teh first post with the Pikes Peak Sabb at 4000m. How much boost does the Saab run at sea level, and what is the power claimed for that? What are the base engine units - are they the same capacity, what rpm do they do at max power?

Edited by Wuzak, 25 September 2010 - 18:26.

[MatsNorway]

I did not say that he had 3.5bar gauge boost at 4000m.

Only said that they claimed 800hp at 4000m.

Here is the full spec on the Pikes peak saab. (not sure about what year this was the spec as he ran twise)

Technical specifications of Per Eklund's Pikes Peak Ecopower Saab 9-3 Viggen

Engine - Original Saab engine block and cylinder head. Engine tuned by
Trollspeed of Trollhattan. Longitudinally mounted, four-cylinder,
16-valve with twin overhead camshafts
- Garrett turbocharger with intercooler (3.0 bar or 42.8 psi)
- Displacement: 2.0 liters
- Bore/stroke: 92/77 mm
- Compression ratio: 9.0:1
HP Rating 750 HP at 8,000 rpm
Peak torque 518 Ib.-ft. at 6,500 rpm
Transmission Four-wheel drive with programmable active differentials and
six-speed Prodrive gearbox

Weight 2,090 Ibs.
O - 60 mph 2.3 seconds
Top speed 155 mph
http://www.trollhatt..._peak_2002.html


Is lbs and psi really the same ****?

kinda like kg and bar? were one is actually a weight unit.

on his page the guy claims even more hp.

Im getting confused here.

http://www.world-rac...tWS2010pr .html

He does not state engine size but on the veichle side he states that a earlier car he made had a 2.4L.

If he only runs 3.5Bar MAP im having doubts about the figures he claims.

Edited by MatsNorway, 25 September 2010 - 19:02.

[MatsNorway]

The Scion spec when he ran FWD in 2007
2007 Time Attack SCION tC
Power:
713whp/703wtq
Lubrication:
Eneos Oil
Tires:
Front: Hoosier 295/30ZR18
Rear: Hoosier 295/30ZR18
Engine:
2AZ-FE 4-Cylinder
JE Pistons
Carrillo Rods
Head:
2AZ-FE
Driveline:
Weismann Differential
Blown:
Bullseye Power S362
Fuel Delivery:
Bosch 720cc Injectors
Bosch Inline Fuel Pump
Golden Eagle Prototype Fuel Rail
Ignition System:
Bosch Spark Plugs
Intake:
K&N Air Filter
Engine Management:
MOTEC M400
Suspension & Brakes
Custom Penske Coilovers
Brembo Race-Spec GTR
Wheels:
HRE 546R 18x10.5-inch wheel

[Wuzak]

Is lbs and psi really the same ****?

kinda like kg and bar? were one is actually a weight unit.

kg and bar are not the "same ****". kg/m² is a pressure, however. Just not the standard units.

Similarly lb is not equivalent to psi. psi is pounds per square inch, and is often written as lb/sq in or lb/in². There are two types of pounds - pound mass (lb) and pound force (lbf). I understand that lb and lbf are directlyanalogous - that is, 1lb mass weighs 1lbf in Earth's gravity.

36lbs of boost! Google told me that was 16.3KG!

Did google really tell you that?

36psi boost is equivalent to 16.3kg per square inch.
Or 25,300kg/m².
Or 0.025kg/mm²

Edited by Wuzak, 25 September 2010 - 20:03.

[J. Edlund]

36lbs of boost! Google told me that was 16.3KG!

what's going on here??

Incorrect use of units is what is going on here. What they mean is not 36 lb but 36 pounds force (lbf) per square inch, perhaps better known as psi, and 36 psi is about 2.5 bar.

This is a Global aka generic OBD II datastream as shown by a typical handheld scan tool. Ign on/engine off, the MAP value is 98 kPa... which to be honest is a little lower than I like to see but is probably normal for this particular vehicle, though it could mean sensor drift or a bit of ground float. At idle the value is in the 50 kPa range, as expected.

There is often an atmospheric pressure sensor built into the ECU, so when the ignition is switched on, the pressure reading from the atmospheric pressure sensor is compared with the output of the manifold absolute pressure sensor, which is used to check the function of the two sensors. There can also be additional checks with the engine running. Some cars also got three pressure sensors with an additional sensor before the throttle. So generally, a modern engine management system is quite good at detecting things like sensor drift.

[T-Mobile]

Boost is just a number, many things must be considered. For instance, my friends Talon runs over 30psi of boost, yet even at 11psi his turbo pushes a much larger volume of air than my WRX's turbo at 17psi.

[MatsNorway]

Boost is just a number, many things must be considered. For instance, my friends Talon runs over 30psi of boost, yet even at 11psi his turbo pushes a much larger volume of air than my WRX's turbo at 17psi.

ye thats right, but i have been watching the street tuner scene for a while and maxed two liter 4cyl "street" engines with 3-3.5bar usually ends up around 800-1000hp

im having doubts this guy somehow manages to be T.H.E MAN on port jobs. by such a staggering margin. we are talking lower boost and more power. slightly bigger engine tho. 2.4L