Engine upgrades - the real truth?

[cyberface]

I've been teased by my dealer with the idea that all I need is a £450 ECU swap to get 260 bhp out of my engine. I have the 240PP Exige, which allegedly already has all the bits required (updated clutch, injectors and fuel pump) to handle the 260 bhp map (because all this change consists of is a remap, by the sounds of things).

We're only going from 243 bhp (or whatever) to 260.

I've saved up for this and after numerous promised 'I'll get back to you' plus something silly to do with a mouse mat, I've had an email saying that the 260 upgrade actually requires *another* upgraded fuel pump so it's very expensive and more fiddly.


Of course this means that my planned booked-in service and upgrade will be cancelled.


However what's the real story (not that I'm not trusting my dealer, but perhaps he's been given bogus information) with the 240PP? There's meant to be an upgraded clutch…. but I've had a few odd 3rd-4th gear full-on acceleration changes resulting in clutch slip (completely impossible to repeat at will). There are meant to be upgraded injectors and fuel pump - but apparently for the 260 I now need *another* fuel pump. Why would Lotus use three different fuel pumps, when most cars will be 220s and only a smaller proportion will be 240PPs and the special Cup cars?

Given that swapping the fuel pump and the (quote) 'obvious cost going up' isn't the cheap no-brainer (given that I'm bound to buy the extra power for £450 but when the cost is significantly more I'd be better off spending it on the serious driver training days, since I'm getting decently quicker now), looks like I'll cancel it.

But what's the story with the aftermarket ECU map changes (i.e. Charlie and the Ronin map) when the car already has big brakes, allegedly big clutch and the bigger injectors. And I'm sure I was told the PP included an uprated fuel pump?


Sounds like it was just misinformation and a bit of a tease really. I'm not paying a grand or more for 20 bhp tops when all I need for another second at Brands is a bit of psychological modification. Power isn't something I'm short of, but if it's cheap, it's always nice to have!

Does anyone know what the real story is here? It sounds like are some corporate inter-department communications issues within Lotus (seen a lot of this in management consultancy roles) so I won't be blaming any particular *people* if I've been given false hopes. But I can't spend too much money on the Lotus because I've got a mad bespoke motorbike project going on right now

[Toyless]

Cant help on the Lotus front, but any update on the bike project ?

[aelord]

That clutch slipping thing on full power, high rev upchanges in 3rd and 4th (and 5th) is really annoying, and embarrassing if you are conducting what is meant to be a demonstration of your superiority to another vehicle. Is it caused by heatsoak into the hydraulics?

The stealer has no answers. Of course it never happens when they test run the car....

[Mr Darcy]

Get the fuel system uprated and you won't hit any issues when conering hard left.

[Scuffers]

it's more than just a map flash to go from 240 to 260.

as you have found out, fuel pump (and the lotus solution is not exactly good here for several reasons), not sure the injectors are not different, the supercharger pulley is different, etc etc.

[aelord]

Scuffers said:

it's more than just a map flash to go from 240 to 260.

as you have found out, fuel pump (and the lotus solution is not exactly good here for several reasons), not sure the injectors are not different, the supercharger pulley is different, etc etc.

I thought the 240 needed new fuel pump and the map only, as injectors are already high flow, and no new pulley?

[STEVEY_SC]

Its well acknowledged that you need an uprated fuel pump when you start to get over 260bhp on the Yota engine. CharlieX who did the Katana and Vision VF aftermarket kits for the Yota explicitly recommends this on his site http://goth.am.

Essex Autosport (Sinclaires) will be able to remap your 240S tune with CharlieX's gotham tune which puts down about 245whp (~260 fly) and frees up the mid-range torque punch. I don't think you need an uprated fuel pump for this. If you want to go higher then as scuffers says you need a smalley pulley (more boost) and better cooling along with an uprated fuel pump. Its pretty easy to hit 300 horses with a charge cooler, pulley and remap.

[Scuffers]

STEVEY_SC said:

Its well acknowledged that you need an uprated fuel pump when you start to get over 260bhp on the Yota engine. CharlieX who did the Katana and Vision VF aftermarket kits for the Yota explicitly recommends this on his site http://goth.am.

Essex Autosport (Sinclaires) will be able to remap your 240S tune with CharlieX's gotham tune which puts down about 245whp (~260 fly) and frees up the mid-range torque punch. I don't think you need an uprated fuel pump for this. If you want to go higher then as scuffers says you need a smalley pulley (more boost) and better cooling along with an uprated fuel pump. Its pretty easy to hit 300 horses with a charge cooler, pulley and remap.

one of the more stupid things about the fuel setup is that they have used a dead-ended fuel system with the regulator in the tank (as is common with most OEM stuff these days), the problem here being the fuel rail pressure is now fixed relative to atmospheric, fine for an NA engine, but start putting boost into the equation, what you get is the effective pressure across the fuel injector will be dropping as the boost rises, thus less fuel (for a given injector timing)
Now, yes you can keep banging in bigger and bigger injectors to counter this, but then the low load and idle becomes a problem with huge injectors, what you really need to do is reference the fuel regulator to the manifold pressure, thus the pressure across the injectors is then fixed and stable, then you don't need huge injectors etc.

Other issue with the std setup is fuel starvation corners when the tank is less than full as it's a single stage pump in the tank.

[Exige77]

I was told standard fuel pump is OK until you start to get close to 300BHP and then it's marginal.

There are many Katana'd cars around 250/60 running around with standard fuel pump.

I imagine Lotus safety margins are more than is required.

Ex77

[Scuffers]

Exige77 said:

I was told standard fuel pump is OK until you start to get close to 300BHP and then it's marginal.

There are many Katana'd cars around 250/60 running around with standard fuel pump.

I imagine Lotus safety margins are more than is required.

Ex77

that's an impossible judgement to make, you would need to know how the 300Bhp was achieved (and are we talking real or 'sales talk' 300Bhp?)

let me put it this way, having flow-tested the std pumps (and uprated ones), no way would I say that they are good for 300Bhp.

FWIW, even with the motorsport one fitted to the 2-11 we fitted a Honda engine to, we used an external high pressure pump as it could not meet the flow/pressure required (let alone with any overhead/margin)

[STEVEY_SC]

Good point on fuel starvation scuffers, happened to me at the new Stowe circuit at Silverstone with one bar of fuel left.

[n17ves]

Scuffers said:

Exige77 said:

I was told standard fuel pump is OK until you start to get close to 300BHP and then it's marginal.

There are many Katana'd cars around 250/60 running around with standard fuel pump.

I imagine Lotus safety margins are more than is required.

Ex77

that's an impossible judgement to make, you would need to know how the 300Bhp was achieved (and are we talking real or 'sales talk' 300Bhp?)

let me put it this way, having flow-tested the std pumps (and uprated ones), no way would I say that they are good for 300Bhp.

FWIW, even with the motorsport one fitted to the 2-11 we fitted a Honda engine to, we used an external high pressure pump as it could not meet the flow/pressure required (let alone with any overhead/margin)

I've got one of the charged cooled 300bhp exiges - Its been verified on a number of dyno including a local dyno dynamics and also sinclaires hub dyno (which made over 270whp) so it best be 300bhp lol.

My experience is the standard pump will cope with 300bhp (just), but is at it very limit at the rpm limiter with no real margin. I would probably start looking at a new pump anything over 270bhp (on an exige s). From what I know, the NA engines do have a different pump to the charged cars so I would expect a katana car will want upgrading sooner. No idea on the flow rates though.

I've been thinking of going down the external fuel pump with a swirl pot - I be interested in know what setups you install.

[Chris_S]

n17ves said:

Scuffers said:

Exige77 said:

I was told standard fuel pump is OK until you start to get close to 300BHP and then it's marginal.

There are many Katana'd cars around 250/60 running around with standard fuel pump.

I imagine Lotus safety margins are more than is required.

Ex77

that's an impossible judgement to make, you would need to know how the 300Bhp was achieved (and are we talking real or 'sales talk' 300Bhp?)

let me put it this way, having flow-tested the std pumps (and uprated ones), no way would I say that they are good for 300Bhp.

FWIW, even with the motorsport one fitted to the 2-11 we fitted a Honda engine to, we used an external high pressure pump as it could not meet the flow/pressure required (let alone with any overhead/margin)

I've got one of the charged cooled 300bhp exiges - Its been verified on a number of dyno including a local dyno dynamics and also sinclaires hub dyno (which made over 270whp) so it best be 300bhp lol.

My experience is the standard pump will cope with 300bhp (just), but is at it very limit at the rpm limiter with no real margin. I would probably start looking at a new pump anything over 270bhp (on an exige s). From what I know, the NA engines do have a different pump to the charged cars so I would expect a katana car will want upgrading sooner. No idea on the flow rates though.

I've been thinking of going down the external fuel pump with a swirl pot - I be interested in know what setups you install.

Just something else to think about. Race cars use an anti surge fuel tank instead of external fuel pump with a swirl pot. This might be more than you need depends on how many trackday's you do. If you're interested check this link and scroll down half way:

http://www.proalloy.co.uk/cgi-bin/sitewise.pl?act=...

Chris

[Mr Darcy]

400 notes get you a uprated fuel system, walbro 255l pump with the fuel rail will easily end any chance of needing to uprate them again. Seems a no brainer to me. Less hassle perhaps than going down the anti surge route unless of course you race it.

[Exige77]

n17ves said:

Scuffers said:

Exige77 said:

I was told standard fuel pump is OK until you start to get close to 300BHP and then it's marginal.

There are many Katana'd cars around 250/60 running around with standard fuel pump.

I imagine Lotus safety margins are more than is required.

Ex77

that's an impossible judgement to make, you would need to know how the 300Bhp was achieved (and are we talking real or 'sales talk' 300Bhp?)

let me put it this way, having flow-tested the std pumps (and uprated ones), no way would I say that they are good for 300Bhp.

FWIW, even with the motorsport one fitted to the 2-11 we fitted a Honda engine to, we used an external high pressure pump as it could not meet the flow/pressure required (let alone with any overhead/margin)

I've got one of the charged cooled 300bhp exiges - Its been verified on a number of dyno including a local dyno dynamics and also sinclaires hub dyno (which made over 270whp) so it best be 300bhp lol.

My experience is the standard pump will cope with 300bhp (just), but is at it very limit at the rpm limiter with no real margin. I would probably start looking at a new pump anything over 270bhp (on an exige s). From what I know, the NA engines do have a different pump to the charged cars so I would expect a katana car will want upgrading sooner. No idea on the flow rates though.

I've been thinking of going down the external fuel pump with a swirl pot - I be interested in know what setups you install.

^^^^^^ what he said. I have similar set up to N17ves with 300BHP. I didn't want to risk it so got the uprated fuel pump. It's not big money.

Ex77

Edited by Exige77 on Tuesday 5th October 11:49

Edited by Exige77 on Tuesday 5th October 11:49

[fergus]

Scuffers said:

the problem here being the fuel rail pressure is now fixed relative to atmospheric, fine for an NA engine, but start putting boost into the equation, what you get is the effective pressure across the fuel injector will be dropping as the boost rises, thus less fuel (for a given injector timing)

I'm not sure how the pressure in the fuel rail drops as a function of boost pressure? Even with a MAP sensor, I've never seen an installation with a variable fuel pressure. Surely for a given pulse width, the injector is open 'X' ms, which means with fixed 'Y' bar fuel pressure, your fuel flow is constant?

I think what you meant to say is that the mixture becomes progressively a lot weaker when boost is applied, rather than "less fuel is delivered" (the same amount of fuel is delievered, but with more air)?

[n17ves]

Although th proalloy tank helps sort the fuel surge issues, but an uprated fuel pump is still required and the tank will need to be dropped to be swapped which is not cheap in it self.

Most guys with the high tuned exiges go for motor sport fuel pump (as fitted to exige 260), which is around £260. This then requires fitting by either dropping the tank or removing the bulk head trim and making the inspection hole bigger. Both options are labour intensive, and fairly costly.

The Walbro is another one that get fitted, but requires slight modifications. The pump can also be very noisy (if wiring stays oem), and is only a single stage pump. I believe all the lotus ones are 3 stage, so the walbro would need some sort of anti-surge system.

I think for high powered exiges, it probably more cost effective to fit a swirl pot and external fuel pump and leave the standard in tank pump in place (certainly for 300bhp anyway).

Edited by n17ves on Tuesday 5th October 14:24

[Herman Toothrot]

Chris_S said:

Race cars use an anti surge fuel tank instead of external fuel pump with a swirl pot. This might be more than you need depends on how many trackday's you do. If you're interested check this link and scroll down half way:

http://www.proalloy.co.uk/cgi-bin/sitewise.pl?act=...

Chris

I've got one of these sat in my livingroom, I must get round to fitting it. I found once my car (on road tyres) got down to showing 8litres I got fuel starvation on hard left handers on track, proper cough and splutter. I'm only in a 150bhp car as well.. Also the great benefit of an extra 10litres capacity, if it works as it says and is fine right down to refill then it should mean I get to do about 20 miles more on track before needing a fill up and about 80 miles more on the road.

Edited by Herman Toothrot on Tuesday 5th October 16:59

[Silent1]

You need to know the flow rate of both pumps to decide whether you really need to uprate it, you may find lotus spec a higher rate pump because the standard one will cope but is within 10% of it's limit and because they're warrantying it they want a lot of built in redundancy.

As for injectors, you want to know how much they're flowing and for how long because you're far safer running oversize injectors for less time than small ones at 100% duty cycle all the time, primarily because if you get any degradation in flow you're going to pink and potentially lunch the engine in spectacular fashion.

[Scuffers]

fergus said:

Scuffers said:

the problem here being the fuel rail pressure is now fixed relative to atmospheric, fine for an NA engine, but start putting boost into the equation, what you get is the effective pressure across the fuel injector will be dropping as the boost rises, thus less fuel (for a given injector timing)

I'm not sure how the pressure in the fuel rail drops as a function of boost pressure? Even with a MAP sensor, I've never seen an installation with a variable fuel pressure. Surely for a given pulse width, the injector is open 'X' ms, which means with fixed 'Y' bar fuel pressure, your fuel flow is constant?

I think what you meant to say is that the mixture becomes progressively a lot weaker when boost is applied, rather than "less fuel is delivered" (the same amount of fuel is delievered, but with more air)?

it's all about the fuel pressure *across* the injector.

if the manifold is at 10Psi boost, the your effective fuel pressure for the injector is reg -10Psi.

now, with 10Psi less pressure differential, you have less fuel flow for a given injector.

your Y above are not fixed that's the point.