lookinco

I have a question regarding boost. So you are saying that boost is created when air is flowing through a restriction and boost will build up as the air is backed up through the restriction. So more air blown through the restriction will cause more boost.

Then why do engines make more horsepower when the boost is higher? Obviously, when the engine are making more horsepower, that means more air is being blown inside the combustion chamber. So that means even though more air are being backed up by the restriction, but more air are still being blown into the engine and produce more power right?

I am only trying to get the concept. I am in no way trying to challenge you. I am only here trying to learn!

Atrain

lookinco,

No exactly. I run 10-psi of intercooled boost on my '95 T-Bird. The car made 325 RWHP/380 RWTQ (SAE) on a dynojet.

Another '95 T-Bird with the same supercharger set-up and engine has ported cylinder heads and a free flowing exhaust. He makes 7-psi of boost and 369 RWHP/399 RWTQ (SAE) on the same dyno.

At 10-psi his set-up made 365 RWHP/390 RWTQ (SAE). Clearly I had more boost than he did yet I made LESS power. As he turned up the boost by spinning the blower faster his power fell off.

If you run a turbo on your car and it generates 15-psi of boost and 500 HP, turning it up to 30-psi would not result in 1,000 HP.

The fact that you have just 1-psi of boost means you have a cork in the system. It is that simple.

Take an Eaton M90 for example. With 14,000 blower speed rpm, 608 c*f*m of air flow and 12-psi of boost takes 50 HP to turn the blower and generates a discharge air temperature of 314 degrees F.

The same blower at 14,000 blower speed rpm, 608 c*f*m of air flow, but only
6-psi takes 33 HP to turn the blower and the discharge air temperature is 217 degrees F.

Thermodynamics law (PV=nRT) comes into play here. The more you compress air, the hotter it becomes. Hot air is less dense (carries less oxygen content) and that means less spark available.

One degree of spark timing on a supercharged engine is worth approx 5-8 HP and 8-10 lb.-ft. of torque. Add 5-psi of boost and you may have to remove 4-5 degrees of spark timing to keep the engine from knocking. What have you gained?
Nothing!

If the supercharged engine is intercooled, then adding more boost pressure can sometimes increase the air charge compression ratio enough to allow more air to be squeezed into the cylinders. When this occurs, you can add more fuel and make a bit more power.

Sometimes adding more boost overcomes anomalies in the intake track and intake enough to allow more air to be compressed into the cylinder.

This is not always the case.

So again, LESS boost and MORE flow made the difference.

A-Train

lookinco

Thanks again for the info!

MichaelBenz

iTrader: (2)

BUt.....wouldnt making more boost on an engine that already flows air fairly well make more power? You cant really compare the internals on a FORD to that of an ACURA or HONDA and make inferences/comparisons from it a whole lot. Huge difference....especially the intake, ect. Hondas flow air WAY better than most any stock domestic and are way more efficient.

I mean....yes....I see what you are saying about boost and flow...and an intercooler, ect. But a high boost pulley alone on our cars WILL result in a gain in HP. Yes....heat is an issue...always has been....but it will create more HP....now your right...as heat builds...it will rob HP....but when you are talking about a drag run....not that big of an issue.

lookinco

Yes, that's what i was wondering about too. It's proven that on similar engine as the TL (Accord, CL), a 8psi pulley will make more power then a 5psi pulley, all on stock internals. Now I do agree that boost is built up when the air being backed through a restriction, but I still believe that when the boost is being raised, more air is packed into the combustion chamber and thus producing more power.

I do also agree that up to a certain point of boost there will no longer be any increase in horsepower because you cannot possible stuff anymore air into the combustion chamber without rasing the temperature too high and detonate.

However I do not believe this situation would happen in the honda 3.2L / 3.5L engine as long as the boost is under around 10psi. There are a few turbo CL dynoed at over 400whp with stock internals (no port and polish). I believe ThinJim's CL-S dynoed at over 460whp with the turbo at 10psi. There is also a CL supercharged at 8psi dynoed at 370whp.

The comptech supercharger at 5psi put out about 300whp. Compared that with the turbo CL-S making 460whp with stock internals, we know that the TL engine is capable of making a lot more power. Of course we cannot compare the power produced between a supercharger and a turbo, but if we are looking only at the engine, we know the engine is capable of making much more then 300whp.

Atrain

MichaelBenz,

I can't stress this enough, you don't want boost you want flow. If you change to a smaller diameter blower pulley (or larger crank pulley) then you will over spin the supercharger. Doing this creates more boost pressure which means more air is stacking up.

The Eaton superchargers do not compress air very well in their housing. They simply paddle it from inlet to outlet. The compression of the air charge occurs from the outlet of the supercharger to the intake and cylinders themselves. This is what makes them so efficient down low and at low boost levels. As they build rpm or generate lots of boost pressure, their efficiency drops off substaintially.

I'm not going to argue with you if you say your TL made more power when you added more boost. However, if your theory was correct then you could add 100 psi of boost and make even more power right?

Once the flow stops...the power stops increasing. Boost is NOT what you want.

Why not? The internal combustion engine is the same regardless if its a Honda or Ford. Spark...fuel...air...compression...POWER.


A-Train

MichaelBenz

iTrader: (2)

But then why does my car make HP continually all the way though the RPM range. Yes...torque decreases at a point....but it makes HP still? Whats up with that? Explain so I can understand...I am with you to a point....here is a visual aid. Unfortunately there is no AFR info on here on the sheet I have in front of me at the moment...but when we are talking HP...at least its listed. Help me understand this concept....

Atrain

MichaelBenz,

First of all, what type of dyno is that? Dynojet, Mustang dyno or other?

What is the correction factor?

Is your car a manual or automatic transmission?

Now the formula...

HP = ( Torque x RPM ) / 5252

240.8 X 6,700 / 5252 = 307.1 WHP

It's no surprise you made good torque which resulted in HP that climbed all the way to redline. Eatons are great for giving linear boost until high rpms.

As far as the dyno goes, it does not measure HP. A dynojet measures how quickly you take to rotate the mass (drums) based on time and engine rpm. The faster, the more powerful the engine. It then gets a torque reading and calculates HP.

The Mustang dyno also measures torque then calculates HP. However a Mustang dyno places load on the drive wheels so the numbers are always lower than the readings from a Dynojet. Mustang Dynos can easily be fooled if you input the incorrect weight.

Dynojets don't care if the car weighs 2,000 or 5,000 lbs. They can be manipulated by installing light weight rims, light flywheel, smaller torque converter, light weight driveshaft (if you are RWD) and such. Less rotational mass means quicker acceleration which a dynojet thinks is more power. Did you make more power at the engine? NO.

Does the car accelerate faster? YES.

In other words, take dyno charts with a grain of salt after all we don't race dynos.

A-Train

MichaelBenz

iTrader: (2)

Yes...it was a dynojet.....as far as light weight rims....I am running OEM rims. I know what you are saying about taking dynos with a grain of salt as they can differ from place to place and type to type (so I have heard anyway....) Now as far as a load on the machine....I remember Joe who was "driving"....and Carey who was manning the controls/pc....and Joe going though the test roll, RPM check and such...and at the same time asking Carey....do you have the load set? So I dont know what the heck he was talking about...but I thought thats what he meant...that they placed some type of load on it? But I am no dyno expert by any means...which is why I was asking you about relating some of the info to the dyno so I could understand what you were saying to some degree. As far as the correction factor...what do you mean....I remember them looking at a few different screens SAE/DIN/among others....and saying something about it adjusting it down to 307.1 because of the temp and air quality, ect or something like that. Does that make sense at all? So I think that was a corrected # or readout you are looking at...seems like one of the other screens said 311HP or something like that....and he said it adjusted it down for conditions. Is that the correction factor you are talking about?

I am not challenging you here...but trying to get a full read and understanding of whats what. I eat this kinda crap up! Was thinking about it all the way home and looking forward to your response...lol.

bklynpanman

where was your A/F at

MichaelBenz

iTrader: (2)

You know...off hand I dont remember and I dont have that printout with me. I do recall him saying it seemed VERY conservative and that we could get some additonal out of it with better ratios which is why we started talking about installing a fuel management system....A FAST system or something like that. Its very expensive though...and off hand I dont know if it comes in a 6 channel system...but I think they do because they put them on Grand Nationals and they are V6...so it should be do-able according to Joe....but it would take some time and most likely some reconfiguring of some things too.

bklynpanman

i ask because i'm running in the 12's and sometimes mid to high 11's.. i had ryan change out my fuel pump and regulator for peace of mind.. i was thinking i was running lean..

MichaelBenz

iTrader: (2)

What fuel pump and regulator did you go with...or did you just switch out to another OEM? Would love to get that automatic into the low 13's to high 12's.

Atrain

MichaelBenz,

You have an auto TL?

Was the torque converter locked up during the dyno pull?

If it wasn't fully locked and was able to slip (they all slip) then your numbers are skewed. The tuner must fully lock the converter through the PCM. We have to do this on the Ford's and it's just a flip of the switch (I/O) in the software.

Your chart looks like it was set to an SAE correction which in my opinion is the best way to go. STD is always 5-6% higher and uncorrected is BS.

SAE bases the results off a given air temperature and standardizes the results.

The dynojet has a fixed load on the drums, he was just stating the load was set. There has to be some resistance or you can actually spin the tires on the drums. I've seen cars with 500 RWHP smoke the tires on the dynojet.

Typically, blower cars require more fuel than N/A cars. A safe A/F ratio with 6-psi of boost is 12:1. That is rich enough to keep you out of trouble. If you go above 6-psi you need to look at a richer mixture obviously.

The extra fuel is there to keep the combustion chambers cool and match the extra air flow. I would not go any leaner than 12:1 with the blower. In fact most N/A cars that rev high will run 12:1 at WOT. This is to protect the catalytic converters which can get really hot.

I think bklynpanman referring to the A/F ratio, not 1/4 mile times.

godfather2

If You're Keeping Your Tl Long Term, Then Go S/c. But If You Don't Mind Parting With It Within A Couple Years, Nitrous All The Way

MichaelBenz

iTrader: (2)

LOL...sometimes a day and a suggestion make all the difference.... I just got what you were saying....I kinda thought that was a little fast for 1/4 mile times....but fell right into it thinking...whoa.....I gotta see if I can get near that neighborhood....lol. I will check later today to see what the AFR is reading out at....again....I dont have it on the top of my hear currently. Only thing I know is what it sits at during idle...which means JACK. (no pun intended Jack) It idled perfectly at 14.7 for a while....but when it got cold out....it went to 14.8 for some reason. Never have figured that one out. Not sure if it was just time installed and something self adjusted or if it was just the cold? But as I seem to remember...when I give it WOT...it goes into the 9's and eventually settles out around in the 12's somewhere too. I will verify that today when I get a chance though.

Excelerate

iTrader: (1)

At idle your A/F ratio will fluctuate generally from anywhere from 14 to 15:1. That is fine. At crusiing speed you may see 13.5 to 14.5:1. At WOT with F/I you should be about 12 to 12.5:1 and at the lower end of that number at peak hp/tq. If you are dipping into the 9's that is way too rich. Too much fuel will wash your cylinders dry and eventually the unburnt fuel will damage your cats.

MichaelBenz

iTrader: (2)

Ok...been watching the wideband for days now monitoring whats what.....here is what I am getting now. (it seems to fluxuate a bit with the weather too). I am all good and just cruising...but on WOT....it now will only go to 11.9 in the cold weather (which is when I seemed to be having the reading in the 9's originally) and right at 12.2 - 12.5 when it gets in the 60 degree weather...right near peak HP levels...so it appears that my system has somewhat self adjusted itself to reality? Kind of odd...cause we didnt do ANYTHING....does that make any sense at all?

LudaChris

Purge is highly recommended. I used to run w/o purge and it takes about 2+ seconds to fully get N20 in the system. It matters a lot when you're head to head.

stillhere153

iTrader: (1)

um this threads almost a year old

KaMLuNg

iTrader: (5)

wow bustedjack...

A-Train u got a TSX now???

Atrain

KaMLuNg,

My wife's '03 RSX was in an accident and was a total loss. We decided to upgrade to a Glaicer Blue 2008 TSX 5AT NON-NAVI. Nice car, not much power, but very nice.

A-Train