How Much Boost on Standard Pulley????

[Smokie]

I just wanted to share my results so far about the kit and maybe get some feedback from other members on what boost levels they are seeing with their cars.

There has been little opportunity to really test certain limits because the weather has been bad the last 3 weeks, today I did some testing and this is what I found out. Getting to 5 psi requires a minor tap on the pedal less than half-way down, getting to 9 psi is also relatively easy, but it requires pedal down 3/4 of the way down.

To get the needle past 9 it requires WOT and the engine rpms need to wind past 4000 rpms, today I had perfect safe conditions for about 15 seconds and I wound out 1st and 2nd gear to the WOT shift points (about 6100 rpms) at the 1-2 shift I was a little past the mid-point between 9 and 10 psi at the 2-3 shift the needle was resting right at 10 psi. After the 2-3 shift the boost gauge needle started to move beyond 10 but the perfect safe window was closing and I shut her down.

I have the stock gears and my rear tires are a little taller than OEM so I think you know why I had to shut her down, redline in 3rd gear is a place I do not want to be. Anyway I have 2 1/2" exhaust and shorties so I expected to have less boost than advertised because of less back pressure is supposed to decrease boost. I have the PHP airbox with stock intake tube and I wonder if my boost would have been higher if I remove the sock or is this about normal, what I should expect?

[DEFYANT]

The stock air intake is restrictive. With the JLT and cold air I can easily get to 10 psi. Your results sound typical.

[Smokie]

The stock air intake is restrictive. With the JLT and cold air I can easily get to 10 psi. Your results sound typical.Do you have OEM exhaust? I think Lidio once stated that opening up the exhaust in our cars would reduce boost because you need back pressure to create boost.

PS: Do you have a sock over your filter?

[MarauderMark]

Do you have OEM exhaust? I think Lidio once stated that opening up the exhaust in our cars would reduce boost because you need back pressure to create boost.

PS: Do you have a sock over your filter?

Yeah but it smells.. :baaa: couldn't help it. :D

[Tallboy]

Smokie,

My car before the K&N install maxed out at 9.5 PSI at 6200 rpm. [My car shifts at 6200] The K&N took it to a solid 10.0 PSI. My lower RPM boost levels are almost exactly as you described in your car.

This morning Carfixer and I completed the install of Trilogy #0087. This is a black 300A with an ASC sunroof, 8700 miles. Quite nice. This car has 4:10 gears, underdrive pulleys [now removed], 180 thermostat, and a tune that were all installed by Dennis. It now has a Lidio tune [obviously] and performs almost exactly like mine does. This car has the stock induction system right down to the paper filter, and we were seeing boost levels a hair shy of 10.0 PSI. Go figure.

[Smokie]

Smokie,

My car before the K&N install maxed out at 9.5 PSI at 6200 rpm. [My car shifts at 6200] The K&N took it to a solid 10.0 PSI. My lower RPM boost levels are almost exactly as you described in your car.

This morning Carfixer and I completed the install of Trilogy #0087. This is a black 300A with an ASC sunroof, 8700 miles. Quite nice. This car has 4:10 gears, underdrive pulleys [now removed], 180 thermostat, and a tune that were all installed by Dennis. It now has a Lidio tune [obviously] and performs almost exactly like mine does. This car has the stock induction system right down to the paper filter, and we were seeing boost levels a hair shy of 10.0 PSI. Go figure.I think an OEM exhaust helps to build boost because back pressure is part of the equation for building boost all else being equal, the only thing I have not checked yet is what the boost pressure is without the Outerwear Sock, I keep mine on all the time and I am curious to know what effect (if any) it will have on boost.

[RF Overlord]

I think an OEM exhaust helps to build boost because back pressure is part of the equation for building boost all else being equal,Javier, I found this in the recent MM&FF article on blowers:

"It's also important, but not critical, to note that screw and centrifugal superchargers compress the air within their housings, whereas Roots blowers force air through the blower and the compressing is done in the manifold."

The way I read this, if the compressing is actually done in the intake manifold, then opening up the exhaust shouldn't have any effect on the boost level. A larger exhaust system will certainly flow more, and help make more power, but I need someone to explain to me how it could affect the boost.

WAG: If the motor has a large amount of valve overlap, I can see a possible change in boost due to the scavenging effect, maybe? :dunno:

[Smokie]

WAG: If the motor has a large amount of valve overlap, I can see a possible change in boost due to the scavenging effect, maybe? :dunno:Thats exactly what I was thinking, the blower is compressing air all the time (during WOT for purposes of this discussion) so when a cylinder is on exhaust stroke and valve overlap the blower is just blowing out the tail pipe sort of speak...right?
The larger the opening to blow out the less pressure...I believe.

Anyway that's my thinking, as flawed as it may be.:D

[RF Overlord]

so when a cylinder is on exhaust stroke and valve overlap the blower is just blowing out the tail pipe sort of speak...right?

This might also account for the small yet noticeable increase in exhaust sound as well? Did you notice the same thing after your install? I think my car is louder than it used to be...at all RPMs, not just at WOT.

[Smokie]

This might also account for the small yet noticeable increase in exhaust sound as well? Did you notice the same thing after your install? I think my car is louder than it used to be...at all RPMs, not just at WOT.
I haven't noticed a change on the vacuum side of gauge, exhaust is louder on the boost side....but the blower is also making some sweet music.....STEREO, sweet.:D

[MikesMerc]

Opening up the exhaust typically results in lower boost pressures. This is primarily due to the engine simply moving more air (and more power). Your engine is nothing but a giant air pump. Opening up the back end with forced induction is a simple but effective way to increase total airflow.

A typical drop in boost on the Trilogy kits with headers and high flow kits is .5 to 1 PSI.

[Smokie]

Opening up the exhaust typically results in lower boost pressures. This is primarily due to the engine simply moving more air (and more power). Your engine is nothing but a giant air pump. Opening up the back end with forced induction is a simple but effective way to increase total airflow.

A typical drop in boost on the Trilogy kits with headers and high flow kits is .5 to 1 PSI.So Mike would it be fair to say you agree with this statement?

Quote by Smokie
Anyway I have 2 1/2" exhaust and shorties so I expected to have less boost than advertised because less back pressure is supposed to decrease boost.

[Tallboy]

Something else to keep in mind-there are also variances fromm guage-to-guage. Not a lot, mind you, but a variance nonetheless. I have swapped guages from car-to-car to prove this to myself.

[Smokie]

Something else to keep in mind-there are also variances fromm guage-to-guage. Not a lot, mind you, but a variance nonetheless. I have swapped guages from car-to-car to prove this to myself.Yes, it's highly unlikely they will read exactly alike, the only remaining question I have is whether the Outerwear Filter Sock decreases boost any, haven't had the chance to check, so much damn rain I don't like to take it off.

[MikesMerc]

So Mike would it be fair to say you agree with this statement?

Quote by Smokie
Anyway I have 2 1/2" exhaust and shorties so I expected to have less boost than advertised because less back pressure is supposed to decrease boost.

A simple answer...YES. I fully agree with that statement. Having shorty headers and a full 2 1/2" exhaust would definitely result in you seeing less boost than advertised...everything else being equal.

Two things to consider.

First, although you are seeing less boost, you are likely making more power than you would at advertised boost levels. Your blower is making the CFM it should be but your engine is just consuming more CFM than a stock exhausted motor so your boost is down when compared to boost levels for a stock exhausted set up.

Second, you might be able to get more boost out of the set without changing the pulley by upgrading the inlet pathway via the K&N kit, JLT, or something similar. If you do this, your not "recovering" any boost....you're only increasing the total cfm your blower is producing now.

[MikesMerc]

Also...about that sock. Although I'm sure it does a good job of keeping the filter clean, it is likely also effecting your boost output. Having the most unrestricted pathway to the blower inlet is key in boost production.

As an example, at Lidio's dyno day a few months back, there was a guy making 1lb more in boost over another guy who had the exact same set up except for one thing. One guy had the stock inlet elbow, and the other had the JLT elbow. Both cars had the same pulley size, throttle body, exhaust mods, and Pro M mass air meter. The only difference was the inlet elbow....and it accounted for 1 PSI. Lidio and I found that to be stunning.

So, lesson to be learned is that the inlet path is VERY critical to boost production. And it isn't like the exhaust upgrade that is actually making more power while showing less boost. When the inlet is restricted less CFM is produced, therefore less boost and less power is the result.

[Smokie]

Also...about that sock. Although I'm sure it does a good job of keeping the filter clean, it is likely also effecting your boost output. Having the most unrestricted pathway to the blower inlet is key in boost production.

As an example, at Lidio's dyno day a few months back, there was a guy making 1lb more in boost over another guy who had the exact same set up except for one thing. One guy had the stock inlet elbow, and the other had the JLT elbow. Both cars had the same pulley size, throttle body, exhaust mods, and Pro M mass air meter. The only difference was the inlet elbow....and it accounted for 1 PSI. Lidio and I found that to be stunning.

So, lesson to be learned is that the inlet path is VERY critical to boost production. And it isn't like the exhaust upgrade that is actually making more power while showing less boost. When the inlet is restricted less CFM is produced, therefore less boost and less power is the result.
I believe the sock maybe robbing me of a bit of boost, what I am afraid of hydro-locking, it is raining a lot down here...I mean a lot. I am surrounded by water.

Thanks for the info Mike.

[Tallboy]

I believe the sock maybe robbing me of a bit of boost, what I am afraid of hydro-locking, it is raining a lot down here...I mean a lot. I am surrounded by water.

Thanks for the info Mike.I drove my car to Ft. Myers Friday, through torrential rains, flooded-over roads, etc. I also went to dinner in a Trilogy car equipped with a K&N that night. It was monsooning on our way home-rain like you wouldn't believe. Neither filter showed adverse effects from the rain-they were both bone dry. No signs of water on the filter at all. I'm not saying all cars will act this way, but I will not be getting a drycharger for my car.

[Smokie]

I drove my car to Ft. Myers Friday, through torrential rains, flooded-over roads, etc. I also went to dinner in a Trilogy car equipped with a K&N that night. It was monsooning on our way home-rain like you wouldn't believe. Neither filter showed adverse effects from the rain-they were both bone dry. No signs of water on the filter at all. I'm not saying all cars will act this way, but I will not be getting a drycharger for my car.
That's great to hear, I may be overly cautious, I know I'm loosing a bit of performance, but I feel more comfortable with the sock on in wet weather. My filter is open and it filters thru the nose which is directly pointed at the air space behind the headlight pod....I will remove it when I go to the track.:lol:

[RF Overlord]

A typical drop in boost on the Trilogy kits with headers and high flow kits is .5 to 1 PSI. Ah-HA! That would 'splain why Lidio's dyno read 8.9 lbs of boost when he did my tune last month. I was thinking it was more due to normal production/installation tolerances...glad to hear it's supposed to be lower...thanks, Mike :beer:

[Smokie]

When I first started this thread, I thought there would be more responses, since there are nearly 90 kits out there and boost levels under different modifications seemed like info worth knowing and sharing.

The response level was not high, but I think the exchange was still wortwhile and Mike stepped up to the table and shared valuable info, so did Mac, Tallboy, Billy and RF. even within some small disagreements, we kept it respectful and informative....very worthwhile in my opinion. Thanks Guys.:bows:

[MikesMerc]

Indeed a good thread. Glad I could lend my 2 cents:)