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Discussion Starter #1
Been thinking allot recently, mainly bought on by repeated quite "modest" rolling road results.

Should throttle bodies increase the rpm at which peak power is made, or should it just increase power over the whole range by X and peak on or around the normal peak.

In my understanding the cam totally governs the power band, i still have the standard cams which realistically are best between about 2000 and 6200.

Ive had 3 rolling roads post throttle body fitting, the most recent 2 have been about 180bhp with a peak of 6k, the first at gerald dale made a peak of around 190-195 at 7k. That was with filter too.

So is gerald dale over reading, or have i really lost 20bhp and 1k of rev range ? Mapping hasnt changed, fuel pressure hasnt changed.

I know the bottom end isnt exactly a spring chicken, but could a slight loss of compression really savage as much as 20bhp ? I fear i might have noticed had i not been progressively lightening the car, maybe masking a gradual powerloss ?

uuuggh, got way too much thinking time these days.
 

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You need to start that porn trade you were talking about and get the money rolling in.

I'll remind you of the 14.3 at the Pod, even with all the lightened interior.

Why have you never been out for a mapping session with Gary or Matt? (Rob is a bit too far North)
 

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Discussion Starter #3
basically cause i dont want an engine map for a shagged piston rings.

Ive never fully understood how you can map a car without knowing whats going on inside the engine, surely it would end up as much as guess of the original map. i.e you need exhaust gas analysis surely.
 

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you need wide range lambda, minimum - otherwise it is just going by guestimates and how it 'feels'

does this latest power run match up the earlier one up to 6k and then drop off ? - regardless of who may or may not be overeading, if peak power has dropped down by 800 rpm something is not right with the latest run - either the engine/mapping/setup has gone off or this latest run was a duffer for some reason - two RRs should always give close results as far as the shape of the curve goes.
 

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I feel, as always that it's not so simple as that, although in general terms, it should not differ too much.

The only reason the power band can change is because of a change in efficiency of the induction system at certain revs.

Thats to say that once you have an open induction system like throttle bodies, the tuned length changes, and becomes more of a factor. The length of the trumpets aids the induction at certain points in the rev range, and therefore there is a disproportionate increase in air intake at, and around that rev point, the shape peaks more.

But in reality, most systems lengths don't seem to be long enough to be tuned into anything where you would see that.

You should see other effects from that too. Just like bunging on an exhaust, or changing the SFi box changes the curves too...

2p worth (well, maybe 1 1/2p!)
 

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The torque curve is the one you need to be looking at. Since throttle bodies are increasing VE you should notice that in most areas it is increased. But as Brian says you have altered the tuned length of the intake system and so the torque peak can move accordingly.
 

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Discussion Starter #8
Alan Jeffery's (peak bhp [email protected]) dec 2002

1000 - neg
2000 - 118lb/ft
3000 - 131lb/ft
4000 - 137lb/ft
5000 - 152lb/ft
6000 - 157lb/ft
7000 - 131lb/ft

gerald dale (peak bhp [email protected]) march 2002

1000 - neg
2000 - 110lb/ft
3000 - 128lb/ft
4000 - 135lb/ft
5000 - 147lb/ft
6000 - 160lb/ft
7000 - 150lb/ft

No graph for BD engineering but peak bhp of [email protected]

6000 - 157lb/ft

-----------------------------------------------------------------------

Ok, so spot the difference, those with keen eyes will see 20 odd more lbs at 7k from gerald dale printout, which is exactly the extra spurt to 7k i was on about. Apart from that both graphs are nigh on identical.

Fuelling maybe? Havent had my injectors cleaned since may 2001, and we all know that MT196 kit is running extremely high injector dwell at 7k.

What would have been nice was to crank the fuel pressure up 5psi and see what happens at the top. Maybe have a play at the SE rolling road day in feb.
 

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its very sensitive to fuelling i have found, i can make the car go like crap with just a simple slip of the pageup button.
i am still not overly sure about the map i have created TBH as Gary said its only been done by feel and things change. heat is the major factor in how the fuelling is determined as well - when starting a hot engine you will notice the idle is lower by around 100 or so revs. this is the engine running lean. so again, a much lower power figure could be due to temps on the runs.
as for the physics read my thesis next year, its all about air flow albeit on the planet, but the maths is the same lmao
 

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Discussion Starter #10
well A-J was from a cold start, probably gave it to him with coolant at 60-70deg. was also run with bonnet up and on a sh-t cold day about 15-17deg, raining outside.

gerald was in march, wasnt cold but wasnt hot, nice day. it was run there with bonnet down, filter on, ambient temp 20deg.

I will get the injectors cleaned and have another run, both can be done at BD.

Have you ever cleaned the air temp sensor ? mines pretty caked up with dust and general induction crud. i have it sitting down the bulkhead infront of the filter.
 

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Discussion Starter #12
thats a nice bit of work, can see exactly what you mean, by rights the peak is 5750 and its downhill all the way.
 

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So is gerald dale over reading, or have i really lost 20bhp and 1k of rev range ? Mapping hasnt changed, fuel pressure hasnt changed.
My opinion Odders is that you should have the car mapped on a rolling road. I think you are missing a bit of power due to non-optimum mapping. The main thing that Mike Warner did when he was interested in engines :)D ) was have it mapped out properly.
 

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Discussion Starter #17
400 quid + VAT for a days mapping.

or 65 quid + VAT per hour..
if you think the mapping or reprogramming can be carried out in a shorter time) This is not usually the case though, problems & delay nearly always happen & almost certainly beyond anyone's control
next suggestion.
 

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ring around, it doesn't have to be steve, I spoke to velos, and they seemed much more reasonably priced.
 
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