How do I get quick/quicker throttle response?
 

I searched a bit and noticed a few threads about bigger throttle bodies and another thread about a guy using a Hayabusa throttle body. What are some things I can do to get pretty quick throttle response? Do I have to do something to my throttle body or are there other modifications that I can do?

Uh, ITB's on a 13BT?

How about a lightened flywheel?


-Ted

You can remove the secondary set of plates, that can help some, but you'll have to learn to perform their function with your foot since they'll no longer be there.

What is the exact problem you are experiencing? When revving the engine, does it stutter for a second and then rev up? When was the last time the car had a complete tuneup including TPS adjustment?

Light flywheel, standalone EMS, and a GT35R turbo if you can afford it. Reprogrammed ECUs and clipped turbochargers are great low-cost mods, but there is only so much you can do with them.

I tested something a while back and im still going to try and make it work.

I disconnected the secondary throttle plates from the primary's shaft so that only the primary would open. This obveously killed power above 2300 but the throttle responce and power below that was incredible. You know that little delay or bog you get when your in neutral and you slam on the gas? That is almost eliminated.
So I have some parts and some drawings and a couple small modifications you woudl have to do to make it work.

BTW. This seem to hurt throttle responce to me very very very little but also seemed to help on the high end. I have 3 spare throttle bodies. 1 S5 and 2 S4. All of which the secondary plates would not open 100% at full throttle. I noticed this was due to the "2 step" system of the throttle body which is a bunch of crap anyways. So if you look on the back of the TB on the secondary plate shaft you will see a little tab that sits between two others. I can take a pic possibly. That tab you bend up so the secondarys open more at WOT. This would also eliminate the 2 step system though which does have a very tiny effect on throttle responce.

By throttle response he is probally talking about the delay in response time from when you step on the gas and the engine produces power. I noticed this delay myself this weekend while autocrossing.

A throttle body may let more air in but I do not think it is going to affect throttle response much by itself.

A flywheel will make the engine speed up quicker and slow down faster while in neutral. It will also increase horsepower slightly. Flywheels are mostly for racing.

Carburetors seem to have better throttle response than fuel injection mainly because fuel is supplied when the accelerator is pushed, while fuel injection has to wait on a response from the airflow meter depending on how the system is set-up. You could also change to a fuel injection system thathas a quicker response time.

Lighter flywheels don't increase horsepower in the sense that they'll help your engine generate more power. They just take away less from what the engine has put out so more is available at the wheels. Same with a carbon fiber driveshaft.

+1^

This is not why they have quicker throttle responce. Infact FI can control fuel much quicker and more accuratly then carb. CARBs, atleast the ones I have worked on. Have spring loaded secondaries which only open under load. So the primary throttle plates open and the secondaries stay closed. You can install different tension springs depending on how early or late you want the secondaries to open. This is where carbs win hands down.

I believe the reason for the throttle responce issue, is due to intake velocity. The intake velocity goes way down when the secondaries open to early since now instead of the vacuum pulling air through one port, the vacuum is pulling air through 2 ports decreasing velocity in the primary port. Fuel atomizes better with more velocity as well.

This goes the same with carburation. Read up on the holly carb web site. They give a good description as to why the secondaries should stay closed and why the throttle responce goes down when the secondaries open to early.

Get a lighter flywheel. That alone will give you better response.

Carbon fibre driveshaft!!! if you have a grand to blow....

Driving style may help reduce the problem of slow throttle response and changing driving styles is free. Use the gear ratios and RPMs to your advantage. Lots of people think that they need to run the engine to the red line in every gear before they shift to the next gear. You need to know where the engine creates the most torque. Then shift at a RPM where the gear you are going into will have the engine RPMs at a point where it is just going in to that peak torque area. If you shift too soon, the engine RPMs fall to low, creating a "slow throttle response" type of feeling. Shift too late, and your next gear will max out sooner, and you will have spent the entire gear on the down side of the torque curve.

Because each gear ratio is different, the shift point will not be the same for every gear.

I have removed 2 driveshafts and I can say that the oem one is very light. Atleast to me. Swapping to a carbonfiber shaft, I can't see making that much of a difference. Especialy looking at where the inertia is located which is in a very small diameter hollow tube.

If I shifted at where my peak torque is. I would be a very slow car. Peak torque would be around 5000-6000 rpm. Maybe a little less. Sorry, but my HP still climbs till about 7500 rpm. Im shifting then.

I have seen many people shift "too early", I can only guess they might be trying to do what you are doing. They are very slow. You and me side by side on the track. I bet, even if you have a stock turbo engine, My n/a would blow right by you on the track when you are shifting that early and me shifting where my power is at around 7500.

Sorry to get back to this thread so late... I have the ACT ProLite flywheel. I guess that's a plus. I have no problems with acceleration for now... considering I am waiting on my turbo to return from BNR. I guess what I am really looking for is that "instant" power when exiting a corner. Like a good touge set-up.

Just to add to my comments above.

The TB can control throttle responce greatly. Drive around at WOT from 2000-5000 and then drive within that same power range, varying your throttle input as the rpms get higher. SO instead of going WOT at 2000-4000, give about 5/8-3/4 throttle and you will notice a difference in power. You will notice more acceleration with less throttle input. Since the secondaries won't be open all the way but the primary will be open more, velocity through the primary is greater.

Airflow velocity, very important.

Depending on what RPM you are at and where your power band ends. Vary your throttle input. Don't go WOT instantly.

Easy fix- Independant Throttle Bodies!

You may want to read and understand the info here: http://www.datsuns.com/Tech/whentoshift.htm

I noticed they talk about shifting at redline. Redline is defined as the maximum RPM the engine should be brought to for reliability reasons.

This is deffinatly not where you want to shift. Redline on S4 is around 7000 I believe and s5 I think is around 8000. This is not where you will have power. On a s4, power will end at around 6200rpm. On a s5 power will end around 7500 or a little higher. This is where you shift or just slightly before. This is just after the peak torque curve. When shifting, the engine will fall just before or at the peak torque curve.

You don't want to shift AT the peak torque curve, you want to shift AFTER the peak torque curve. The article even says this. Infact, what you were saying in your original post, is you want to shift AT the peak torque curve which contridicts what the article is saying.

pic of a torque curve similar to mine. Except mine goes a little further. This is a S4 with the S5 Mani.
http://www.globalvicinity.com/images....9577_2807.jpg

I actually don't think this will fix the issue. Although I have never used ITBs. I think it would make it worse, but I don't have experience in this area.

125 shot of nitrous should do the trick

For my $0.02 I have found that advancing the timing to 5 degrees BTDC (leading) and 10 degrees ATDC (trailing) gives the best throttle response (with a carefully adjusted TPS and idle fuel mixture.)

A cone filter helps some, but not as much as the timing.

For the record, I think that the reason that the 13b seems to have throttle lag is the volume of the intake runners between the throttle plate and ports (2-3 rotor charges in each.)

Sorry Rota, looks like, albeit in a very confusing way, he said what you're saying a few posts ago.

My driving style is trying to maximize the largest area under the power curve, since everyone knows that power is what actually moves the car. Apparently, a drag racer friend of mine disagrees with me. I don't know, I usually shift after the power peak to maintain the most area under the power curve. He tells me something about momentum and to see what happens if I shift a little earlier say 7100 rpms instead of 7500 rpm.

Intuition tells me that maximizing the power under the curve vs. shifting where drive torque in one gear equals drive torque in the next gear seems to be the same thing. You always end up shifting after the power peak. I could probably prove that statement if I had an hour or less.

More power if going to make the car feel more responsive.
Now, it's up to you to shift the transmission to get the engine into it's powerband.

"Lugging" the engine from too low of an RPM will of course make the engine feel sluggish.
Getting the engine into the revs will greatly increase its responsiveness.


-Ted

The flywheel does increase the engine brake Horsepower because it is one of the engine components. Driveshafts and rims will increase your wheel horsepower. The flywheels returns are directly related to the engine speed and the wheels and driveshaft will be related to the road speed based on what gear you are in.

Lightened parts require less force to accellerate so there is more force that can be used elsewhere. If by more power you mean more energy out of the combustion, then yes it does not change this but then neither does lighter rods, pistons, and crankshaft.

So you're telling me that if you hook up an engine dyno to an engine, take one dyno run, then pull the stock flywheel and put on the lightened flywheel, you'll make more on the the second run on the engine dyno?

Last I checked, flywheels were part of the drivetrain, as opposed to the engine.

My statement was referencing the combustion effects of adding a flywheel as opposed to adding things like nitrous, bigger port, or turbo. I would think that the difference with the lightened flywheel will not show up on an engine dyno, but will show up on the wheel dyno. I would imagine that the power peak on the wheel dyno would be the same, but there would be slightly more power along the curve.

I would imagine you're correct; lightening things like the flywheel will increase the engine's ability to accelerate, and acceleration is one of the factors when calculating HP. Anyway, I'm not an expert, but I do know this:

HP ~= mass * velocity * acceleration

Actually, I don't think acceleration has anything to do with it...

http://www.g-speed.com/pbh/torque-and-hp.html


-Ted

port and polish the throttle bodies
 

i've heard of some people porting and polishing the trottle bodies out to gain low to mid range torque increases is this true ??

sorry about the poor grammar im fixing a coolant leak and trying to write lol

He was also contridicting himself. IF you read his entire post, he says to shift AT the peak torque curve so the RPMs fall at the peak torque curve which is impossible.

He then decided to argue with me saying I was wrong by saying shifting at your peak rpm with power. On my engine, thats around 7500-7800. My peak torque curve would be around 5500-6000. Why shift there?

How is that possible?

It does. There's the familiar torque * rpm method, but there's also the mass * velocity * acceleration method. I've used this method myself with awesome results. From the g-tech site (http://www.gtechprosupport.com/support/HP1.htm):

edit: in case you're interested:

v=d/t
F=m*a
W=F*d
P=W/t

P=m*a*d/t
P=m*a*v

Hmmm...interesting...
Cause acceleration can be manipulated through gearing.
The formula does not take into account gearing.

You'd get two different results when doing a 1st gear run versus a 5th gear run?


-Ted

Exactly, the peak HP values would be the same between the two runs, but the time it took to get there would be different. For a car, that formula tells you wheel HP, not engine HP. Aerodynamic drag, etc. is also baked into the result, so it's more like "usable HP" than wheel HP, and will usually be lower than dynos because of it.

Is "v" defined as "terminal" velocity at the instantaneous time when you're trying to calculater horsepower?


-Ted

I believe you would do runs with the Gtech just like you do on a dyno. 4th gear runs at 1:1 ratio.

Ted, if you were referencing my post earlier, my point was that

bhp X hp loss due to drivetrain = whp

All a lighter flywheel or a carbon fiber driveshaft would do is lessen the hp loss. However, I have no proof, but I believe the loss savings will converge to zero as rpm and hp get closer to the hp peak. That's just my intuition speaking there.

....

Quote:
Originally Posted by Project84 https://www.rx7club.com/images/buttons/viewpost.gif
Then shift at a RPM where the gear you are going into will have the engine RPMs at a point where it is just going in to that peak torque area.

That is what I said. I think you are getting hung up on the part that I highlighted in orange.

I never said "shift at the peak torque curve so the RPMs fall at the peak torque curve". The only way that would be possible is if the two gears had the exact same ratio. You completely fabricated the statement, then decided to say that I said it and that contadicting myself and arquing with you. You need to re-read my post, understand it, and stop trying to stroke your giant internet-ego or what ever it is you are doing because I was not and I am not trying to argue with you.

Instantaneous everything. It looks at HP, acceleration, mass, and velocity at a particular instant. If you logged HP over time, calculating HP continuously with that formula, you'd get what looks like a stretched/squished dyno graph, but with unknown RPM.

edit: if you did a smooth zero- to redline- run

Your right, I must have misread your post and some how thought you said to shift at your peak torque.

YAYE! FREE MODS! I always tighten up some of the slack on the throttle cable because they come conservative from the factory for average usage, but since you want more response just get rid of a little bit of slack and you will see a difference. Also it's easier to get out of first, at least to me it was because there are alot of hills around my area.

Sorry, you're right.
I keep getting confused, cause I automatically assume velocity is a derivative fraction of distance over time. :P
You can get instantaneous velocity at one point.
Stupid "dt" kept pointing me in the wrong direction!


-Ted

Before this gets too heavily into torque, gearing, etc., I'll give the simple answer. Shift to maximize horsepower. The answer to all the torque, gearing, etc. calculations will equal horsepower. As for acceleration, acceleration = power / (mass * velocity). Lighter cars accelerate faster and you accelerate quicker at the top of 1st gear (~40mph) than you do at the top of 2nd (~60mph), 3rd, etc. You don't get infinite acceleration at near zero velocity b/c your power is also near zero.

As for throttle response, there are two things to quicken: foot to throttle body and getting the air from outside to the engine. That may be why newer cars are drive-by-wire: quicker throttle response b/c you don't have to deal with the stretchiness of a cable. Might also be quicker b/c of computer control on the throttle, I dunno. Advancing the timing makes the spark plugs fire sooner, so I suppose that's why that would improve throttle response. But, like most tuning, that's not the best thing for the longevity of your engine.