Impul Throttle Bodies

semtex · 05-21-2009, 02:51 PM

So . . . what does running these do to our USDM reflashes (when they become available)? Anything?

wstar · 05-21-2009, 03:01 PM

Quote:

Originally Posted by semtex

So . . . what does running these do to our USDM reflashes (when they become available)? Anything?

I'm sure a good dyno tune shop can account for these with good software. What I recall from my LS1 days is that an oversized (vs stock) throttle body will tend to lean out the engine without the ECU knowing about it, so it can be potentially dangerous without a retune.

The MAF on the LS1 was calibrated for a given TB diameter. If you oversize without adjusting the ECU (or somehow adjusting the MAF output), the MAF output is actually wrong, and it's giving bad data to the ECU. I don't know if the ECU's data from the header-mounted wideband O2's can help it adapt or not, but I wouldn't want to be the first to try without knowing more.

Edit: Actually I'm pretty sure it would be a bad idea without a tune. The widebands might tune for it at idle or cruising throttle, but IIRC at WOT the ECU is going to ignore those inputs and use a preconfigured map, which will run the car too lean given the bad MAF input.

370Ztune · 05-21-2009, 03:15 PM

Quote:

Originally Posted by wstar

I'm sure a good dyno tune shop can account for these with good software. What I recall from my LS1 days is that an oversized (vs stock) throttle body will tend to lean out the engine without the ECU knowing about it, so it can be potentially dangerous without a retune.

The MAF on the LS1 was calibrated for a given TB diameter. If you oversize without adjusting the ECU (or somehow adjusting the MAF output), the MAF output is actually wrong, and it's giving bad data to the ECU. I don't know if the ECU's data from the header-mounted wideband O2's can help it adapt or not, but I wouldn't want to be the first to try without knowing more.

Edit: Actually I'm pretty sure it would be a bad idea without a tune. The widebands might tune for it at idle or cruising throttle, but IIRC at WOT the ECU is going to ignore those inputs and use a preconfigured map, which will run the car too lean given the bad MAF input.

Great feedback

. This is one of the main reasons why until recently, Impul was only offering these throttle bodies with the ECU.

-Hunter

t-ray · 05-22-2009, 10:10 AM

I just can't see any need for larger TB's, not unless you are pushing some major air through the system. And if you're doing that, you're force inducted, and the entire intake tract is pressurized, so I don't think the TB's would really have any benefit.

Can someone please explain this to me?

05-21-2009, 02:51 PM	#1 (permalink)
semtex A True Z Fanatic Join Date: Jan 2009 Location: Behind enemy lines Age: 56 Posts: 5,995 Drives: People to drink Rep Power: 34	So . . . what does running these do to our USDM reflashes (when they become available)? Anything? __________________ "There are no small accidents on this circuit." -- Ayrton Senna 316.8whp & 248 ft/lbs (Dyno Dynamics) \| 319whp & 256 ft/lbs (DynoJet) (04/23/10) Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

Thread Tools
Show Printable Version Email this Page
Display Modes
Switch to Linear Mode Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
How's the Drive-By-Wire (DBW) throttle?	JTso	Engine & Drivetrain	32	08-22-2010 11:28 PM
New IMPUL Front; Ver.2	370Ztune	Exterior & Interior	11	05-22-2009 11:59 AM
Impul/Sachs Coilovers	370Ztune	Brakes & Suspension	0	05-21-2009 02:37 PM
a LOT of new Impul Goodies!	370Ztune	370Ztune	0	05-21-2009 02:35 PM
Intake manifold / throttle bodies	wstar	Engine & Drivetrain	14	04-15-2009 11:55 AM

05-22-2009, 10:10 AM	#4 (permalink)
t-ray Base Member Join Date: Apr 2009 Location: bham al Posts: 91 Drives: 05 g sedan 6mt Rep Power: 18	I just can't see any need for larger TB's, not unless you are pushing some major air through the system. And if you're doing that, you're force inducted, and the entire intake tract is pressurized, so I don't think the TB's would really have any benefit. Can someone please explain this to me?