What is "throttle response" really

The term "throttle response" is thrown around alot. It is often said that a low compression engine will have poor response. I don't see anything magical about higher compression other than it simply produces more torque everywhere. So here are my questions.

You have two engines. One is a 500cid engine with 7:1 static compression ratio. The other is a 300cid with 11:1. Which one will have better "throttle response"?

The next comparsion is between two 300cid engines. One has 7:1 compression, long running intake, small heads and small cam. The other has 11:1, single plane intake, huge heads and huge cam. Which one will have better "throttle response"?

My logic tells me that in both of these examples the engine with lower compression will have better "throttle response" because "thottle response" is synonymous with low speed torque and in both of these examples the lower compression engine still has more low speed torque. What say you?

Everytime I drive a rental mini van with a small engine that has 10:1 compression it is a dog.

 

Re: What is "throttle response" really

Well if you were saying that it's purely whichever has a higher torque number, then you're correct but there are probably a few ways someone could define it. Some would say it would be how quickly an engine recovers vac. on throttle tip in. That would probably be my definition if I was trying to define the term itself in a blanket way for all engines.

 

Re: What is "throttle response" really

I would say that it has to do with reciprocating weight also. Just changing from a heavy stock converter to a lighter smaller one can produce better "throttle response" on most engines.

 

Re: What is "throttle response" really

X's 2. I used to run a dirt sportsman car that had decent throttle response. It had 11:1 compression a direct drive transmission(no converter) but cheap heavy internals (claimer rules), 2 barrel intake and a holley 500 cfm 2 barrel carb. I had the chance to drive a modified car a couple of times and I can tell you they had way better throttle response. They ran the same cubes, about the same comp. with solid rollers, same transmission with good heads and lightweight internals. They were set up with big single plane intakes and holley 750 dp's that were worked to flow more.
I am by no means and engine builder and maybe it was a combination of the recip. weight and the extra power that made the difference.

 

Re: What is "throttle response" really

I would say lighter parts equal faster acceleration. For me, I lean a little more toward a throttle tip in to vacuum per time equation. Or, on newer drive-by-wire vehicles, the lag between tip in and computer to engine response. I am not sure of an official or updated definition.

 

Re: What is "throttle response" really

I got an 8:1 408 with a neutral balance. It has almost too good throttle response.

My 1985 MR2 with a 7500 RPM does not have very good throttle response, at least below 5200rpm.

Throttle response to me is rate of engine acceleration in relation to throttle position in while free revving or before the converter stalls up.

Anything else while driving is just relation to gearing, speed, torque.

 

Re: What is "throttle response" really

Sounds spot on to me.

 

Re: What is "throttle response" really

lets not get mixed up by comparing an engine that 'makes a lot of torque' with an engine that has good throttle response.

You can have a 500 cid engine with 8:1 compression feel like it has throttle response, just because it makes relatively large amount of torque.

we have to first define what is throttle response, and I believe it the the response time between when your body sends a signal through the gas pedal to the engine to do something, and it then does it. That interval of time, is throttle response, regardless of how much torque the engine makes.

 

Re: What is "throttle response" really

I think that the plenum size could influence throttle response. If there is a lot of volume between the throttle and the intake valve then when you snap the throttle open it takes a little time for the vacuum to be replaced by air at atmospheric pressure. You need to accelerate all the air in the induction system to start filling that volume.

ITB's on the other hand minimize this volume and most sports bikes used them with resulting excellent throttle response.

 

Re: What is "throttle response" really

http://en.wikipedia.org/wiki/Throttle_response

Throttle response
From Wikipedia, the free encyclopedia
Throttle response or vehicle responsiveness is the responsiveness of the vehicle to throttle (accelerator pedal) modulation. When the accelerator pedal pressed suddenly, how fast power output of engine increases implies the throttle response of that vehicle. Throttle is not used in diesel engine, but the term throttle often refers to accelerator control. Throttle response is often confused with better power, but throttle response is rather related to time taken for change in power level.[1]
Generally [gasoline]/[petrol] engines exhibit better throttle response over [diesel] engines. Also naturally aspirated gasoline engines have better responsiveness over supercharged and turbocharged engines. Here comparison should be experienced in engines which have same peak power output. Several tuning factors have an effect upon the responsiveness of the throttled engine.[2][3]
Throttle response in manual cars can be enhanced by dropping to a lower gear (eg 5th to 4th) just before an overtaking maneuver and is often utilised in smaller cars to aid in overtaking maneuvers
Most new cars are equipped with a drive-by-wire system. Throttle response is often affected badly by this and drivers feel a noticeable delay when quickly changing the position of the gas pedal.[citation needed]
[edit]Application of throttle response

Throttle response comes into play in the following:
Overtaking
After following a vehicle or going side by side, there is a need for sudden increase in power to execute a successful overtaking. This is why throttle response plays a crucial role in racing.
Coming out of a corner
While entering a corner, brake is applied or at least power is reduced. As soon as the corner is passed, the car should be accelerated quickly. Better throttle response gives a sudden surge in power.
Driving pleasure
Throttle response plays a major role in driving pleasure, as this gives the driver more control over the vehicle's acceleration.
[edit]See also

Driving
Throttle
Overtaking
[edit]Notes and References

^ "DIY: Free and Easy 2005+ Mustang Throttle Response Modification". autobglo.com (Auto B Glo). 2007-11-14. Retrieved 2008-01-19.
^ Bohacz, Ray. "Eliminate Engine Detonation Without Losing Power and Throttle Response". highperformancepontiac.com. Retrieved 2008-01-19.
^ Kowatari, T.; Aono, T.. "Throttle-control algorithm for improving engine response based on air-intake model and throttle-response model". IEEE Xplore (IEEE). Retrieved 2008-01-19.

 

Re: What is "throttle response" really

So most don't equate good "throttle response" with good low speed torque.

Nothing seems to support the statement I often hear that "low compression hurts throttle response".

 

Re: What is "throttle response" really

I can tell you it does not with a v8. Or at least in my experiance.

Now 7.6 or 7.8:1 4cylinders suck and are lazy.

I guess my 408 could be snappier, but then it would be impossible to drive without lighting the tires up at every intersection or hill.

 

Re: What is "throttle response" really

I didnt read the replies so excuse me if someone already touched on this.

Comparing what you did above is comparing apples to oranges.

Compare apples to apples.

Take a
Built small block chevy 350 cubic inches make it 12 to1

Take the same 350 above make everything Identical except Make the compression 7 to 1

And you will see a perfect definition of throttle response.

Throttle response Is the amount of revs over a given time from 0% throttle to instant wide open throttle.

Here the poor 7 to 1 sucks. So lets change the heads to a smaller head and smaller cam smaller intake with longer runners. Now we have better throttle responce but less power. Now we are back to comparing oranges to apples.

 

Re: What is "throttle response" really

Just responding to Andy's post. In my 408, low comp did not hurt throttle response one bit and it is not my definition of Lazy or bad throttle response at all.

The 7:1 four cylinders I've driven have taken awhile to rev once WOT. All have been turbo engines and doggy off boost.

Not really sure if your picking apart my post or just making a point that low comp engines can be snappy.??

 

Re: What is "throttle response" really

This is exactly the point.