Project Q - Sams 86 (many tech Pics)

[rthy]

riojin: before I say anything what engines have you had experince with first hand in th ecar that made you feel like it lacked low down torque?

not for show: If F1 engines used wider angles the head would be a little wider yes but it would also be quite lower because the inlets wouldn't be so long anymore. I dont think it would add any extra weight also.

As for the valves:

4age

inlet: 29.5mm
ex: 25.5


4/7afe

inlet: 31mm!!
ex 24.5mm

also the well known Bill sherwood is also building up one of these engines and he has fitted 33mm inlets I think by memory. Looking at the chamber theres stacks of free space ofr bigger valves. How much material you can take away from the inlets to have the right cross sectional area is another story.. However there is enough to suit 33mm valves so that should be enough for anyone.

[riojin]

im used to 6 cylinder cars like a mk3 supra with a 7mgte and a mk2 with a 5mge conversion. when jumping into a 4age 20v ae86 (not my own car) i was suprised on how different you have to drive it compared to a mk2. the 5mge outputs about the same power as a 4age 20v but the torque difference are quite huge. the both weigh about the same. this to me made me feel like the 4age 20v didnt have enough torque.


i cant really explain what im trying to say without a curve diagram but ill try.

in relation from rpm to power output and rpm to torque output and the comparison of the 2 show the period where the max torque hits is usually before where the max power hits.

eg on a blacktop 4age 20v the max torque hits at 5600rpm and max power hits at 7800 rpm

this is in relation to circuit driving (grip) and my personal driving style

the closer these 2 are together the better for accelerating out of a corner. taking corners before the max torque rpm is suggested when cornering. to progressively shift you throttle higher (progressively give it more revs) is also recommended. doing so shifts you closer to the max torque rpm (to go over this range is not reccomended) and closer to the max power rpm. so you are gaining torque and gaining power.

with an extended rev range between the two rpm max points, you can take a corner at a certain speed but not necessarily accelerate out of it. it takes too long to get to the required revs to quickly gain speed.

so this thereby makes your corner exiting slower. this brings me back to a comment made earlier on what kind of engine youre trying to make and the style of driving youre planning on doing.

my theory is that when you push your engine to gain more power the way youre trying to it will lessen the torque output or atleast shift the max torque output further away from the max power output so the useable power when cornering is too low.

a good example of this is the f20c out of a 2003 s2000. revs high and has amazing power for a 4 cylinder but the amount of useable power when cornering is lowered because of the distance between these max outputs, which makes the engine slower whilst cornering. the design of the s2000 is made to compensate this by being ultra light weight and not in theory needing as much torque, but this has proved false seeing honda decided to raise the displacement to 2.2L to give it the more torque which was lackng whilst keeping the same power output.

again it all depends on how you like to drive

much of this will sound like gibberish and im sorry, im sleepy. if you want something clarified ill try to explain it again when im not half asleep

[rthy]

ok this is tricky, if you like the feel of the low down power output of the 5M engines then your probably out of luck with an A engine but knowing what I know this is what I would build for you:

* 7A bottom end
* 4-2-1 pipes that have a 1 meter primarary length and 600mm secondary length (long!!!)
* intake length about 50mm longer than a standard 20v
* ported, but not opened up
* standard comp ratio
* aftermarket ecu
* cold air duct
* maybe a custom cam with 230 degree duration with 8.5mm lift on the intake and 8mm on the exhaust? (I dont know that much about cams)

now the head:
* 20v head (vvt helps with mid range power) or
* 7afe cylender head with the standard inlet and exhuast port area with also deshrouded combustion chamber and light porting.


With all this you may still end up with 120kw or so but your mid range would be huge, I dont know if its what you would be looking for though



As for the cornering being slower this is dont understand. I find all I do is keep my revs very high to compensate. During a set of twisies it wouldn't not be uncommon for me to hold the engine at 6000 between two tight corners. This way I am able to have the torque there so that I can control my car well with the throttle. Also I think S2000 cars are well known for cornering well. However I do see why you would want lower torque as it makes it easier to drive agressively.

Lasty dont beleive what they say about that F20C engine, its a heavy engine, how do I know? well lets just say my friend actually weighed it. I think he got 170kg with the accessories on it. But I guess thats still not too bad considering the power.

anyway keep asking questions as I am happy to try and help.

[riojin]

what you said about the type of engine you would build me is what i am planning to build in the long run. for now im just gonna grab a 4agze for the easiness factor seeing is a stock engine with decent torque. my ae86 is my daily and i dont want something thats gonna cause too much problems/have bugs to be ironed out; which could result from building a hyrbid engine.


what i mentioned about the cornering ill try to explain a little better.

the inertia forces involved when taking a corner gets absorbed/counter-acted but 3 main things. 1-the structural integrity of the car and the shocks, 2-the tyres, 3-the engine.

the items in group 1 being the suspension setup absorbs some of the inertia forces as does the cars chasie ability to move, all act in the same kind of way to counteract the inertia forces. these in a race setup are usually very firm so they absort some but most of the forces has to be counteracted by the tyres and the engine.

the tyres grip at a certain rate which lowers over time with the more forces you put on the tyres. not usually a loss of tread but more of a loss of tyre pressure which is worse.

when driving a circuit you dont want to change your tyres too often because this will cause massive losses in time's. so driving to save your tyres is beneficial. this is done by extending corners so the inertia forces acting on them arent as harsh, and by using your engine to counteract the inertia forces. in short the amount of torque you engine can output is what this is determined by.

if you are using a progressive throttle technique (allows you to gain speed out of a corner) when driving through a corner you are gradually giving it more revs. the highest ammount of torque in the rpm range is the best place to be because the engine is countering more of the forces and putting the least possible strain on the tyre pressure.

if you go past the max torque output in rpm you are gradually taking away what the engine is doing to counteract the inertia forces and gradually putting more strain on your tyres.

so in the long run if you keep pushing past this max torque output point you cornering ability will lessen because of the lack of tyre pressure.

so to keep yourself from doing this you make sure you give your tyres the least amount of strain as possible by keeping the revs under the max torque rpm.

this brings me to my point. say on *engine z* (imaginary engine for the sake of the explaination) has a max power of 100hp@6000rpm and max torque of 90nm@4000rpm. using what i said about about trying to keep your engine reving at the max torque rpm for taking a corner means rev it to 4000rpm. this engine when reved to 4000rpm wont be producing its max power. it will obviously be less. say for example 65hp@4000rpm. this means that the most speed gained on the exit of the corner is determined by 65% of the max power.

but if you have *engine y* with 100hp@6000rpm and 90nm@5000rpm, it will produce maybe 85hp@5000rpm which is 85% of the max power.

so by making an engine rev higher and/or have more power without changing the displacement (or doing something else) to get better torque, cornering ability will be greatly effected

[ae71]

there are other ways to change the power and toque charictoristsi of an engine, other than changing the displacement as im sure you well know. tuning, cams, length/diameter of intake and exhaust ports/maifold.

would you say generally when a engines safe RPM level is increased and power levels take advantage of this that the toque would also rise to higher RPM? but then again i surpose you have to balance the points i made above between touqe and outright power..

i think i understand what your saying riojin, i have experience this felling and now i have a better understanding of why. i thought it was just because i had braked correctly and taken very good lines with the right corner speed. i also like to use the thottele out of the corner as you mentioned sam, my tyre setup also helps the car to turn and give a good exit (alsong as its not uphill or it bogs down in wheel spin). i thourouly enjoy reading threads such as this and i have learnt alot from Sam. but this is getting a little off track from the engine build comments.

a silly question but with a wide angle head would you have a smaller length port from valve to manifold? or is the head phisicaly narrower over all on a narrow angled head, making little diffrence?

[rthy]

riojin: I think I get most of what your saying but the way I see it is that I can afford to lose a bit of tread and when I go past the max torque revs I would still more than enough torque to acheive maximum cornering so at all times I would need to control it with the throttle.

By the way when you asked about an engine for you I thought you meant na and I described an all out approch. For atmo still I think an ae112 7afe with decent cams, modified inlet manifold and an aftermaket ecu might do wonders. Other than that I think you shouldstart and end with a 4agze, maybe boosted, they ae torque kings

Aaron: not a silly question at all because not many people would think of it. A narrow valve angle head either has a very stangely shaped side on it (never happens) or the inlets are unsually long. When I say inlets I mean valve to the manifold face. I will post a picture up on here shortly. The heads are narrower but because they enter so high up theres no way around this easly.

[riojin]

sorry for draggin my comments off-topic. i love this thread btw

sam=good bloke who definately knows what hes talkin about

i vote this thread be made a sticky

[ae71]

dose the longer ports have an effect on perfomance? i would of thought that shorter ports would be better becase there would be less distance for the gases to travel.

[rthy]

riojin: thanks but you got to be carefull, nice maybe but I am just another guy who is trying to figure out what is good and what isnt, and I dare say that when it comes to engines its mostly just research, a huge amount. I am just saying I might get it really wrong and I can admit I am very nervous that my 4a hybrid engine will end up being a total slug in performance.

Ae71: the length of the ports are no so much important as the shape, from my understand if the ports are straight in the last section it means that theres less resriction around the valve stems and also it uses all the valve to flow air instead of mosty one side with an angled port. But I could be mistaken. The length isnt important because there has to be a set length from the valve to the tip of the trumpet, so if the length is shorter in the port I just have to make up for it in the length of the manifold if that makes sense. The only other factor I can think of is that the injector placement must be further away which affects things.

Update: today I was looking where I can bore a hole in the side of the head and also where I need to take meat out of the combustion chamber, its going to be tricky

[ae71]

Sam why would you need to bore a hole in the side of the head unless your putting a direct port nitrous kit in? lol...




...oh maybe you are heheh