Part Throttle Vs Full Throttle Engine Response

[kyepan 291]

Hi there,

 

Suddenly occured to me today that i drive around on very little throttle most of the time (i guess most people do), and for the most part the MI is bloody excellent, loads of torque for a mere tickle of the throttle from very low down. This makes it thoroughy nice to drive around, nippy, but without a big fuss. Time and time again I read posts that the "nicest" MI's to drive have little more than 3 angle seats and slightly upped compression. this gets me wondering. All the people that get bodies, management and a big cam say "loads of torque" are driving around with their right foot planted cause they have just had their engine breathed on, but what happens when the go back to daily driver mode and how does it really effect your 80% of time spent pootling behind grandma to the shops. This brought up the following questions.

 

 

Do throttle bodies, especially short ones that are not curved and angled like the mi \ 6 \ s16 inlet kill the lazy drivability or meerly tune a particular part of the rev range better and preserve all the low down stuff?

 

Do reshaped ports, throats and combustion chambers only work at high speeds, or once again are they a uniform improvement across the rev range.

 

Same question with valves

 

same question, and i guess a more obvious answer for cams.

 

Just trying to clear up in my mind where to go next with the engine.. because as much as i like a good blat, it's never going to go on the track (prefer karting) and will 99.999 % of the time be a daily driver and b road monster.

 

I guess we all agree a well mapped after market ignition system is going to improve drivability some what...

 

J

Edited November 27, 2007 by kyepan

[danpug 1]

Throttle bodies generally produce more power throughout the rev range. My mi16 on bodies had loads of torque, a gentle press of the throttle was all that was needed to cruise up steep hills. Cams will move the power elsewhere, i'd say you would lose some of your low down power as a sacrifice for power higher up.

[pee vee 1]

throttle bodies and a map give pretty much the best throttle responce you will get..

 

However,, dont think many people have a TB set up on a standard head and cams... and its the bigger cams which will

take some of the 'driveablility' (lower down in the range) that you talk about (i'd say).

as they do tend to move the power peak further up the chart.

 

But raised compression will make the car feel more snappy too.

[brianthemagical 1]

basically yes, and no. ever wondered how you can get a screamer engine that produces lots of power or a similar basic engine that will produce more torque. it's all in the engine tuning and mods. so if you want lots of low down torque, you modify the enigne to get it. it is different than high bhp tuning as you only need so much air, so allowing more in won't help. custom bodies will increase throttle responce as metioned above but you can design the manifold to give the engine lots of torque low down, around a certain rpm. same with the cam, lots of lift, but short duration to ensure a good dynamic compression. but you will lose topend. most mods, like cams, will have a given power band, in the same way it goes up, it can go down. i would have thought you'd struggle to get too much off the shelf, but good luck, nice to see someone not just bolting bits on to give more power. or fit a turbo.

[Sandy 189]

This is much of the difference between top notch headwork or just porting for "flow". The point about the inlet is very important too, I would say the majority of multiple TB set ups are just bought as what fits and bolted on either without much thought or because it's what the big name tuners use; but to work well you need to experiment and develop the set up to suit that particular engine. Mapping and ECU choice is another issue, there's no standard for mappers and seeing a well mapped car is the exception, rather than the rule. How many mappers properly road test or cold start the car after? But even the best mappers have to make a compromise on the time available to do the job!

 

Moderation and taking a broad view, is usually the key to a flexible and pleasant tuned engine.