With Silencer vs. Without silencer dyno numbers

[Rwick7]

It seems there are several different views on this subject so I thought I would give my analysis. I do not have a scanner so I'll hand type everything...hopefully it doesn't get all jumbled.

29.74 in.hg
71.8 F
Correction Factor 0.98

First run was after about a hour sitting in parking lot then second run right after silencer removal. With fan about 3 feet away from front of car.

RPM w/hp wo/hp w/tq wo/tq tq difference

2200 124.3 127.2 296.8 318.1 + 21.3
2300 133.2 135.1 304.2 322.5 + 18.3
2400 141.4 142.8 309.4 326.1 + 16.7
2500 149.1 150.0 313.2 328.3 + 15.1
2600 156.9 157.7 316.9 331.2 + 14.3
2700 164.5 173.8 320.0 338.1 + 18.1
2800 172.5 180.7 323.6 339.0 + 15.4
2900 180.4 189.0 326.8 342.4 + 15.6
3000 188.7 197.6 330.3 346.0 + 15.7
3100 197.4 204.8 334.4 347.0 + 12.6
3200 205.5 211.9 337.3 347.8 + 10.5
3300 214.0 218.6 340.5 347.9 + 7.4

Okay this is taking tooooo long.

from here up here are some stats

hp least increase - 0.4
hp most increase + 6.1

Tq least increase + 0.3
Tq most increase + 5.1

At 3900 and 4000 the silencer shows a 0.4 hp increase in both instances this is the only point on the graph the silencer show gains.

I'm not sure what this all means. Probably mostly it shows the inaccuracy of dyno's and how not to bet the bank on there results.

The first run was the first time the car had been taken to redline...so maybe it loosened her up a bit for the second run? I'm not sure but either way my silencer is stayin off until I get a CAI.

 

[Elapidae]

This is what I was pointing too in another thread. Many people do a "cold run" with the silencer in as their first run then with the car warmed up, they pull the silencer out for the second run and see an increase.
My theory was that if the Dr. is correct, then what this shows is that the car will run better when warmed up "not hot mind you". So, had you left the silencer in for the second run, it might have even been higher. :shrug:
Maybe not. :shrug:

I know I can go from one dyno shop here to another and get 15 rwhp difference (I've actually done this). So I try to take any numbers that show 15 hp +/- with a grain of salt.

 

[Rwick7]

I agree...different dyno's but on the same dyno, strapped in the same, same day 5 minutes apart? I would say +/- 7 tolerance would be a wash. Either way there just dyno numbers...and a CAI is still better. So who cares just buy a CAI...now which CAI...that is up to the good Doctor.

 

[slythetove]

I did 3 runs.

2 with silencer

last without

with:

368.4 HP
366.7 HP

without:

374.4 HP

 

[jmir018]

i remember a thread (CAI shootout) where people said that you actually lose hp by removing the silencer...i am so confused and dont know who to believe now..

 

[Rwick7]

I know...it's all so confusing...I'm not sure what causes these variances.

 

[dmreitz]

It sure looks like there is a lot of debate on this subject... it seems to be based on past experiences with different cars, supposed statements made by Ford, dyno numbers from different cars that are in direct contradiction with one another, etc. Some people say that Ford may have designed the silencer specifically for the airflow characteristics, or whatever...

Let's look at what we know for sure...

1) The "air intake silencer" is definitely designed for at least one reason - to silence the intake of air into the engine (the name pretty much says it all).

2) This has been a popular modification to Mustangs in the past and supposedly has accounted for some minimal gains in power in the naturally aspirated engines. The supposed gains on previous models are not the issue however - the fact that the modification has been popular is the reason people started doing it on the 03 Cobra.

3) With the air intake silencer in place you draw cooler air from outside the engine compartment. With the silencer removed, you draw air from within the engine compartment - though it is somewhat shielded from the engine and will come somewhat from the fender - it should be warmer than the air that is drawn through the silencer - but probably not as warm as if the entire air box is removed.

4) Assuming the dyno reports are accurate, there have been cars tested that have shown power gains after removing the silencer, and cars that have shown power losses after removing the silencer.

Ok, based on the above information only, I think we can draw the following conclusions:

A) Removing the silencer makes the air intake louder

B) There don't seem to be any MAJOR gains or losses from removing the silencer. Most of the dyno numbers seem to be pretty close (loss or gain).

C) Based on the conflicting dyno numbers, and assuming there are no other real variables that were changed when the silencers were removed, it seems that the probable reason for the conflict in dyno numbers is most likely atmospheric conditions (including temperature of the air that was drawn into the engine).

One way to put this to rest is to take some of the cars that claimed gains, and some that claimed losses, bring them to the SAME dyno shop at the SAME time and submit them to the exact same test conditions (whether that be running the engine for 5 minutes before the first dyno run, or icing the SC down, or whatever - as long as they are subjected to the EXACT same conditions, it will be a fair test). If this is done, and the cars all show losses (or gains), then we may want to try different test conditions to see if we get an opposite affect. If, however the cars still give varying results (even under the same test conditions), then it would seem that for some reason, each car simply reacts differently to this modification (some gain power, some lose). Perhaps this is because of differences in the computer reaction to the change, or because of other issues we've seen like clogged cats or what have you.

Ok, so what does all this mean? It probably means that removing the silencer doesn't do much at all (good or bad) to the power of your engine... but if you feel good about doing it, then do it!!! If not, then don't!!! It's your car!!!

:beer:

 

[ronreid03]

What if I hook up my autotap and run WOT with and without the silencer? Would it show that more or less air was going through the engine? It seems to me it would but what do you technical types think?

Ron
03 Yellow Convertible

 

[[iSEPIC]]

Only way to be sure is to run 2-3 runs w/ then 2-3 runs w/o then 2-3 runs with then 2/3 runs w/o then chart that.

 

[SonterraSVT]

StlBlack03,

Black Coupe

Stock Dyno
368.5 rwhp
355.2 rwtq

How come your dyno stats are low compared to other `03 cobra stats for RWHP and RWTQ?

 

[Elapidae]

Originally posted by dmreitz
<snipped>One way to put this to rest is to take some of the cars that claimed gains, and some that claimed losses, bring them to the SAME dyno shop at the SAME time and submit them to the exact same test conditions (whether that be running the engine for 5 minutes before the first dyno run, or icing the SC down, or whatever - as long as they are subjected to the EXACT same conditions, it will be a fair test <snipped>

I agree completely and just want to make one observation. Generally when you have your car dynoed, you have the hood up. This is not a real world driving scenario (I hope) for most people. I think this is significant in this discussion because the cooler air that the non-silencer airbox could pull in would not be so cool with the hood down. Just an observation though. I know that with the car moving the air dynamics under the hood are fairly unknown. :shrug:

 

[Weasel]

I'm sure that the differences in air movement in the engine compartment vs the fender would be hard to get a handle on in respect to a real driving situation and it's effect on performance. But I just had a thought about temperature in these two locations. Has anyone used one of those remote temperature sensors in the fender vs the airbox location to see how hot it really is there when driving ?

Mike