didn`t know my coupe revved to 7000

I hear what you are saying,but it is a simple fact,the more you push the power higher up the rev range the less accessable/useable it is.

One of the coupes strong points, is the fact it has fairly good torque low down, and all thro the rev range,i want to keep my torque curve as flat as poss, but with as much power as poss, from as low as poss.

It would be very easy for me to bolt on a big turbo and get almost 500bhp but I`d have no low down grunt at all...................
I don`t think that would make it

a/ a very fast road car and
b/ a nice car to drive

I would be happy to say my coupe makes over 450 bhp,but not if i have to rev the nuts off it to find the power

I really dont think you get my point.

(7000 rpm is because people who tune will probably raise the rev limiter a bit - most chips do)

Please tell me why it is so much worse to rev 6000 rpm than it is to rev 5000 rpm ?

Why wouldnt it be a fast roadcar? maybe it would be a little slower in first gear between 10mph and 20mph, but do you really need to go that slow?

I dont think you understand that it doesnt matter what kind of torque range the engine have unless its geared for it.

The only thinkg you really do by moving the shift points lower down the rev range, is that you lower the speeds at wich you gear. And in return you loose top-speed.

No it wouldnt be easy. Not if you want to keep the torque band between 4000-7000 rpm.
(Sure you could get 500bhp with a big big turbo and torque starting at over 5000, but that would make your car pretty slow and inefficent because you cant rev to more than 7000)

At those powers the deal is not just about switching turbo and have a lot of power. To get a bigger turbo to spool up as fast as a smaller turbo. You need a more efficent engine.

People on this forum get to that point in two ways.
Some alter the cylinder size. (The "easy" way)
Other start porting and matching and play with different cams etc. (the hard way)

And some do both ;-)

With all due respect you're wrong.

A turbo doesn't spool at an arbitrary rpm. On higher gears it will spool up earlier, so the forum uses pretty much spoolup in 3rd or 4th as reference, so if a turbo is fully spooled up by 4000rpm in 3rd you will go off boost switching up between 1st and 2nd. Or at least you will be in the rpm range where the turbo is still spooling up and so you will hit a flat spot between gears.
Trust me I used to have a turbo that spooled up at 3800rpm in 4th but 4300rpm in 1st and about 4150rpm in 2nd and unless I changed up within 200rpm of the std redline it would drop off boost.
Plus if you have any sort of wheelspin in 1st or 2nd when you change up you will definitely go off boost because the revs on the rev counter will not reflect the revs as delivered to the tarmac.

Fuel, by you going into gear ratios and this and that your WAY off the mark again.

Paul doesnt drive around in 2/3/4th gear most of the time. Also who wants to be driving on boost with a big turbo at 4000rpm in 2nd gear? The characteristics of the larger turbos is a severe kick in the arse. Smooth power delivery available on tap is the setup that Paul wants (and myself really).

Regardless of what revs your gonna end up with when ya switch down, your still having to use the high end of the rev range.

Btw if i wanted to know the torque band you'd think was ideal, i would have asked. However, i was more interested in the actual figure you would deem to be good for acceleration. From what i know about Paul's car from Barbz, Paul could EASILY get any high end figure he wanted from the 2 litre, because of the extensive headwork on his car. So he could get 450bhp with spool up *around* 4000rpm.

Whether he wants to drive to an ON/OFF car is the question.

Ross

yes I feel that way too,but due to work load just now,no further forward tbh.



I might just invest in a second turbo,and have 2 live chips written, one with the maps for rsr, and the other mapped with a bigger turbo,then I can have both.....

not fast enough !! change the turbo and chip.........

to much lag, change back

JohnS: Correct. But in what way does this make me wrong? I never said "Get a turbo that has full boost at 4000rpm in 3rd gear" I said "get a turbo that doesnt spool up much later than 4000rpm" And by that I mean in any given gear. (If you however have full boost around 4000rpm in 2nd gear you're pretty safe for the rest of the gears)
Wheelspin in 1st and 2nd gear is not really a problem since it can be eliminated with good software. (mapping, traction control etc.)

I myself have a "bigger" turbo. With spoolup around 3800-4000rpm. And I can say that even with those rpms (wich you think are horrible) im wasting a lot of low end torque.

h2ypr:
? If he wants to drive around and cruise in fifth gear at highway speeds it wont be a problem. I really dont understand what you think the problem is here.
There is nothing ON/OFF about a larger turbo, you just move the torque band.
I think what you are after is a car with 1 gear wich will always have quick response. The way combustion engines work right now this is not possible. (Not unless you want to sacrifice acceleration/topspeed - maybe on cars with electrically controlled valves)
Electric cars however, have this kind of torque delivery (constant torque) and dont need any gears. Hopefully we will see a lot more of those soon. (Tesla roadster)

How much xxx BHP paul can get with his mods are pure speculations, all im saying is it wont be a "walk in the park". And if done right it wont be an ON/OFF car as you describe.

And by the way, gearing is probably one of the most important things to think about. Even with an engine who only has a torque band between 3000-3100 you can make it fast. (continuously variable transmission)

It is the compromise between flexibility and outright power. If you look at rally cars they have a reasonably wide power band and that is because there are situations where it is better to utilise the current gear rather than change down etc.
In general you can measure flexibility by calculating the areas under the horsepower graph. The greater the area the more flexible the setup. Flexibility means it can perform well across the range and for everything except straight-line dragging I think it is important.

Just wana comment something here..i have a GT28R and im suffering form the turbo lag!

If I floor it on first up to red line and I drop it to second, the car is feeling lazy until it reaches 4800-5000rpm! During that short time any car could pass me! I have tried to do as much as I can to reduce the lag, but it seems that no way to do it. (check my graphs here )

I would agree with john, that I would get the boost in 3-4 before I see it in first and second, maybe its due to boost controller or something but it annoying me. TBH many times am thinking to fit superspool or hybrid to improve the spooling.

What I want to say is that its important to reduce the lag and have the power at te same time get compromised solution, but just don’t drop any one of them.

omran

If you want the best of both worlds, you need to go for a different ECU. One from Omex or DTA will allow you to fully map the fuel, ignition, build in traction control using the ABS, limit the boost in 1st and perhaps 2nd, and allow a much greater control then a standard ECU which has been mapped. Omex for example allows the use of a bigger Turbo, and with enhanced head work etc, can even incorporate launch control and have anti lag as well.
Why you guys insist on keeping the old ECU i cannot understand. Spending so much money having your engine built with forged parts and heavily modified engine parts, this will limit its potential. No matter how good you map the original ECU [even with a chip], it is always a compromise somewhere in the rev range.

Andy.

Good point Andy.

We can actually get very close bhp figures for my engine with a gt28rsr or a few of the bigger turbos, solely because it has been done before,so in this instance we do have a very good indication of bhp figures.

I don`t want a power band that starts at 4000revs + ,no matter how it is put, it is not as fast on the road as an engines who`s power comes in at say 3000rpm,unless of course you drive around in a gear lower than you would normaly need, or be prepared to change down every time you wish to be in the power band,do you drive around with your engine spinning above 4000 rpm all the time ?

For instance,on the new 997 GT2 Porsche has worked hard to get peak torque from 2200 rpm to 4500,which helps to make the thing so rapid,squeeze the throttle and your off,not squeeze, wait until you get past 4000 rpm, and then go, or have to change down all the time...............buy a Honda for that

Yes, I do agree with the correct gearing, you can then alter every aspect of how the car will respond/behave,I am not in an economical position to do that,or fit variable transmission.

It`s down to trying to get the best compromise between outright bhp and driveablity,and having all the power above 4000 rpm just does not cut it for me,also heat+high revs are a big killer for any engine,so 7000 rpm, I don`t want to have to constantly be their, to go fast.

Fuel have you got a Fiat Coupe ?

Paul - Slight point about the GT2, it uses Variable vane turbos, so can allow boost from very low down, where as we cant

With Omex for instance, you can have a switchable map, so it can run several maps. Just have it at a flick of a switch.
Even the standard Turbo is more then a match for the standard engine. It can provide boost to over 300bhp easily. Its how the engine uses the boosted air mass. Making the head more Volumetric Efficient is the key to good reliable power. Just bolting a big Turbo and chipping the engine, and hoping for the best is a recipe for disaster. A few members on here can adhere to that !!
As for revs, OE rods are good for around 7500 revs max. Forged are required for more revs. Also because of the way the crank rotates the rods, you need to be careful how you build the bottom end.

Andy.

JohnS: Yes, this is a good cause for torque low-end. Rally cars however as you describe it make the band "wider". Not loosing high-end torque. A wide band is always good, this is not the cause here though, since by making the coupe have full boost at 3000rpm you move the band lower down. (not making it wider)
You tradeoff high-end torque.

Omran: After watching your torque curve, you seem to have peak torque around 5500rpm, and a big drop earlier. This makes you way of band and thats why you're experiencing bad acceleration/driveability.
I really cant see the boost curve so I cant comment this any further. Your car will probably be a lot faster after you fix this.

sumplug: Very very true. People can have the best hardware there is, but if there is nothing to control it reasonably it wont be noticeably better then a std car.
With good software you can adjust the ignition curves better when off boost and kind of remove the "lag feeling" a bit.

paul:
Maximum acceleration is always obtained when the torque at wheels is max.
Torque at wheels will always be larger on the coupe at lower gears. So even when you have torque low down and dont have to shift down when at 3000rpm - a car who has torque range higher up and does shift down, will leave you behind because it will have an higher average torque at wheels.

Yes. I have a coupe. A 16VT.

No I don't run at 4000rpm in 2nd gear when I dont need it, if im just cruising around im almost always at 4th 5th gear at almost any speed. When I want to have fun I downshift, turning the rather silent car into a race machine.
If im racing, I keep gears low and revs high. Wich gives me instant response and great acceleration.

Nope, you cannot have torque at both ends of the rev scale. Torque is measurable under the torque curve. Its the duration and lift of the cam[s] that determine your torque curve. Remember on a 4 valve engine, air velocity is low at the bottom end against a 2 valve engine due to the valve size. A turbo helps to increase the velocity but the static compression is low. Until the air is boosted, the measurable dynamic compression is low, then shoots up when boost comes in, velocity shoots up, torque shoots up and so does power.
So a rally engine would rev say 2500-7500 revs, whereas a race version of the engine would rev 4000-9000 revs. We are talking usable power.

Andy.

if you are talking about complete maps that you can interchange even with the engine running, you can do that on the marelli ecu (16vt) for 30euro (twin map adapter and chip from moates.net) or 40 or so for 8 maps (which I personally find pointless)

V.

Fair enough, but on a modified engine, the OE ecu will never be able to be optimised unlike the aftermarket ecu's. On the Omex for instance, you can have over 2000 different maps!!
Just think of it this way, you build the engine to take high boost, but you want to run most of the time at normal boost. so you have a optimum map that runs your car as standard. Yet, flick of a switch, it can run high boost, again with optimum mapping. Advantages, are better fuel consumption, additional traction control, anti lag, launch control, over boost facility, and the best bit, its interchangeable between none Coupe cars!!

Andy.

Andy, you are right I don't think anyone will argue against that, however

cost of installation together with sorting out all the various sensors that need replacing (crank, temp, map, maf, you name it...), testing and time on the RR tuning it we are talking some serious money right?
It's not 1 or 2 grand for forged rods/pistons and the paraphernalia needed. Again if you are keen on traction control and fancy stuff like that the balance moves back your way

V.

Omex can be ordered with bespoke wiring loom, so it will fit pretty easily. Its not that dear to buy,, certainly well under £2000 to buy and map, but you can use it on any car you choose. Over say 2 years, if your mileage is reasonable, it will save you quite a bit in fuel costs, as other cars with Omex, are excellent on fuel !! If needed, you could also sell your Omex and the market would dictate an easy sell too!!

Andy. \:\)

Anyone would think you're trying to plug Omex a bit?

But can it do 5 cylinder sequential firing? That's the trouble, most aftermarket ECU's cant, it's either 4 or 6 cylinder, not 5, hence why people keep the OE ECU

Hi Alexis. Yep, both the new DTA and OMEX can do sequential. We have one fitted to a Punto HGT, and its running fine. Can do 5 cylinders as well. This is the baby.
http://www.omextechnology.co.uk/Ecus/710/omem710.htm

Andy.

yes beggers I knew that , I was just pointing out that Porsche who are virtualy able to do as they wish,or as they have the means to,has not stuck all the power high up the rev range, but has made it available from VERY low revs,and have a very very fast driveable car.
and no i`m not saying it`s not fast high up the rev range too, the turbos` used allow this ,but they hve still chosen to have the max torque range between 2200-4500 revs

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Here is my question tho andy.

The supra comes with a twin turbo, but most of the high power ones are a single turbo. So obviously there is a disadvantage to having 2 turbos. Is this a move in the right direction?

Ross

Supra have small twin turbos blowing sequentially. I want to blow a small one into a big one, there generating fast spool up and increased density. It will also take up less space.
Or maybe a Supercharger blowing from idle to 4500revs, and Turbo from 4500-8000+ revs.
The electronics are out there as shown by VW, but sticking a Supercharger on has its space problems. Possibly space to put it is where the Aircon pump sits.
Its all pie in the sky until we actually decide to go ahead and build a fast Coupe. My partner has Jaguaritous at the moment, so its all jags being done.
Plans are to have a race XJS next year, and it may appear at TOTB if finished in time.

Andy.

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O/T

But since you posted it, 2 large turbo's (but smaller than 1 larger one) will still produce the same power as the single large one. Just more expensive to do as you need 2 of everything.

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Post deleted due to claiming work that is untrue