Is it bad to quickly let off the gas?

Rotary Rasp · 02-02-2011, 03:01 PM

Anyone who has a DCI knows what I'm talking about. (especially with a tune)

I find my self quickly letting of the gas to produce that whoosh sound. I installed my JB4 last night and enabled the boost on fuel gauge. I can see the boost spike when I do it. Is that bad for my car?

Ilma · 02-02-2011, 03:32 PM

When you close the throttle plate boost builds up in the chargepipe and creates a spike which is then released via the diverter valves.....which is the wooshing sound you hear.

Since the throttle plate is shut, the engine does not see the spike at all and you are safe.

Some of the boost gauges read pressure in front of the throttle plate so it will register on such a gauge, but the engine is not seeing it.

Other boost gauges tap into the intake manifold pressure post throttle plate. If you see a spike on that type of gauge, then the engine is seeing it too.

Perhaps the Burger folks can clarify where the JB4 reads boost pressure from. If it's the TMAP sensor the it's reading pressure in front of the throttle plate.

Tee212 · 02-02-2011, 03:34 PM

No

Forcefed3 · 02-02-2011, 03:36 PM

Thats not bad at all.

Rotary Rasp · 02-02-2011, 03:55 PM

Awesome. Now I can do it with joy!

hipnotic · 02-02-2011, 04:34 PM

shouldn't be a problem

FoShizzle · 02-02-2011, 04:34 PM

Quote:

Originally Posted by Ilma

When you close the throttle plate boost builds up in the chargepipe and creates a spike which is then released via the diverter valves.....which is the wooshing sound you hear.

Since the throttle plate is shut, the engine does not see the spike at all and you are safe.

Some of the boost gauges read pressure in front of the throttle plate so it will register on such a gauge, but the engine is not seeing it.

Other boost gauges tap into the intake manifold pressure post throttle plate. If you see a spike on that type of gauge, then the engine is seeing it too.

Perhaps the Burger folks can clarify where the JB4 reads boost pressure from. If it's the TMAP sensor the it's reading pressure in front of the throttle plate.

Very informative! I was wondering this myself.

sleepergm · 02-02-2011, 09:52 PM

No problems ... But if you hit it too hard to redline and then let off the gas you might throw a flame out of your exhaust ... I have done that a couple times by accident.

roozie2001 · 02-05-2011, 04:51 AM

yes u should never let off the gas. havent u ever played need for speed??

Infamous · 02-05-2011, 09:41 AM

Quote:

Originally Posted by sleepergm

No problems ... But if you hit it too hard to redline and then let off the gas you might throw a flame out of your exhaust ... I have done that a couple times by accident.

LOL are you catless

O-cha · 02-05-2011, 12:33 PM

Quote:

Originally Posted by sleepergm

No problems ... But if you hit it too hard to redline and then let off the gas you might throw a flame out of your exhaust ... I have done that a couple times by accident.

Quote:

Originally Posted by Tee212

No

Quote:

Originally Posted by gbreeE90

Thats not bad at all.

Quote:

Originally Posted by josh06lau

shouldn't be a problem

Actually letting off the throttle sharply under certain conditions is bad for your engine. Specifically high load and the higher the RPM the worse. Sharply letting off at that point is extremely hard on the connecting rods as the load on them is suddenly reversed, it very easily blows older engines up.

Newer DBW cars hold the throttle open a little bit before closing completely though.

skinrock · 02-05-2011, 12:36 PM

Quote:

Originally Posted by sleepergm

No problems ... But if you hit it too hard to redline and then let off the gas you might throw a flame out of your exhaust ... I have done that a couple times by accident.

And now when you do it, they are no longer "accidents" right

Juiced46 · 02-05-2011, 03:48 PM

Quote:

Originally Posted by O-cha

Actually letting off the throttle sharply under certain conditions is bad for your engine. Specifically high load and the higher the RPM the worse. Sharply letting off at that point is extremely hard on the connecting rods as the load on them is suddenly reversed, it very easily blows older engines up.

Newer DBW cars hold the throttle open a little bit before closing completely though.

The load is suddenly reversed? Its not like the engine spins the other way. lol

This statement is entirely false. Under high load it is not bad to let off the throttle abruptly. There is no ill effect. The load goes down but it doesnt reverse. It will not blow your engine up either, I do not know where you got this type of information but I would love to see it. There is far more stress on your rods, under WOT and high RPM then there is when you close the throttle.

mycoupe · 02-05-2011, 05:11 PM

Why do people ask questions like this? I mean cmon, common sense people.

02-02-2011, 03:01 PM	#1
Rotary Rasp Lieutenant Colonel 243 Rep 1,857 Posts Drives: 2009 E92 335i 6MT Join Date: Aug 2008 Location: SoCal - Torrance iTrader: (6)	Is it bad to quickly let off the gas? Anyone who has a DCI knows what I'm talking about. (especially with a tune) I find my self quickly letting of the gas to produce that whoosh sound. I installed my JB4 last night and enabled the boost on fuel gauge. I can see the boost spike when I do it. Is that bad for my car? __________________
	Appreciate 0 Tweet Quote

02-02-2011, 03:32 PM	#2
Ilma Colonel 195 Rep 2,855 Posts Drives: 2023 M4 Competition Join Date: Nov 2008 Location: Mississauga iTrader: (0)	When you close the throttle plate boost builds up in the chargepipe and creates a spike which is then released via the diverter valves.....which is the wooshing sound you hear. Since the throttle plate is shut, the engine does not see the spike at all and you are safe. Some of the boost gauges read pressure in front of the throttle plate so it will register on such a gauge, but the engine is not seeing it. Other boost gauges tap into the intake manifold pressure post throttle plate. If you see a spike on that type of gauge, then the engine is seeing it too. Perhaps the Burger folks can clarify where the JB4 reads boost pressure from. If it's the TMAP sensor the it's reading pressure in front of the throttle plate.
	Appreciate 0 Quote

02-02-2011, 03:34 PM	#3
Tee212 Banned 81 Rep 4,541 Posts Drives: yes Join Date: Oct 2008 Location: Riverside iTrader: (9) Garage List 2010 335 [8.00]	No
	Appreciate 0 Quote

02-02-2011, 03:36 PM	#4
Forcefed3 Banned 132 Rep 4,732 Posts Drives: 2008 335i Join Date: May 2010 Location: South iTrader: (2) Garage List 2008 335i [1.00]	Thats not bad at all.
	Appreciate 0 Quote

02-02-2011, 03:55 PM	#5
Rotary Rasp Lieutenant Colonel 243 Rep 1,857 Posts Drives: 2009 E92 335i 6MT Join Date: Aug 2008 Location: SoCal - Torrance iTrader: (6)	Awesome. Now I can do it with joy! __________________
	Appreciate 0 Quote

02-02-2011, 04:34 PM	#6
hipnotic Major General 153 Rep 6,603 Posts Drives: e92 335i Join Date: Oct 2007 Location: So. Cal iTrader: (7) Garage List 2008 335i coupe [7.00]	shouldn't be a problem
	Appreciate 0 Quote

02-02-2011, 09:52 PM	#8
sleepergm Lieutenant 44 Rep 541 Posts Drives: White 335i M-Tech Join Date: May 2007 Location: Hong Kong iTrader: (2)	No problems ... But if you hit it too hard to redline and then let off the gas you might throw a flame out of your exhaust ... I have done that a couple times by accident.
	Appreciate 0 Quote

02-05-2011, 04:51 AM	#9
roozie2001 Just some guy 49 Rep 1,531 Posts Drives: 2008 White 335i sedan Join Date: Apr 2008 Location: Houston, TX iTrader: (4)	yes u should never let off the gas. havent u ever played need for speed?? __________________ 2008 BMW 335i/Sedan/Alpine White/Terra/Steptronic/Premium Package/Sports package/Comfort Access/USB/Sirius
	Appreciate 0 Quote

02-05-2011, 05:11 PM	#14
mycoupe Banned 60 Rep 1,495 Posts Drives: 07 335i coupe 6spd Join Date: Dec 2009 Location: cincinnati, Ohio iTrader: (5)	Why do people ask questions like this? I mean cmon, common sense people.
	Appreciate 0 Quote