We had spectacular results, improving power and torque using less fuel. We made a few modifications to the air intake, which made the car run leaner and closer to ideal air fuel ratios, being 13 to 1.







John Penlington

Unique Auto Sports

 

That's fantastic... care to tell us what you've actually done?

Or have I missed another thread somewhere?

 

Bit of a trade secret. It took us a while to figure out.

 

Sounds interesting! I'm no expert, but if you simply modify the air intake, won't the ECM's adaptive fueling function simply adjust injector on-time to bring the mixture back to 14.7:1?

Cheers,

Don

 

So you start with 216.25 KW (290 BHP) and end up with 162.6 KW (218 BHP) ??? I must be getting something wrong here, because the way I am reading this is, that after your modification you end up with 25% roughly, less power than you start with ? Assuming ( and that's always a dangerous thing ) this is rear wheel BHP not flywheel, then how much power does the gearbox ,diff and drive shafts actually rob ? Please don't get me wrong, I am not trying to put you down or demean your work, I am just confused... can you please explain. Thanks in advance, Andy

 

Welcome to the forum John.

You should stop by our new members area & introduce yourself New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

In answer to Andrews question, the dyno definitely shows power at the rear wheels.

218rwhp is about right for a 16 year old car that supposedly had 290hp at the flywheel from the factory.

Losses of about 20% could be expected through the drivetrain, maybe more, maybe less.

When it was brand new it might have done 230hp at the wheels or so.

 

Unless I missed it but it could be a 3.2 which was what 240ish BHP when new?

 

potentially you could modify the maf sensor and bypass air around the hotwire, so esentially
letting in unmetered air, ie leaning it out...the computer can only adapt to a change it sees via the hotwire in the maf......
just my theory....2cents

unless this motor uses a map sensor, which i don't know about

 

You don't have to modify the MAFS to allow unmetered air into the intake: just open a joint anywhere in the intake plumbing after the MAFS. But if I'm not mistaken, an air-fuel mixture of 13 (parts air) to 1 (part fuel) is _richer_ than the standard Lambda 14.7:1 mixture the ECM adaptive fuel metering wants to maintain. Since the ratio of air-to-fuel is lower, the ratio of fuel-to-air is higher.

 

Sounds about right. My XJR was 276kw from quoted figures, but was dyno'd a couple of years back at 240rwkw. You'll always see a lower figure on a dyno than the manufacturer claims

At least they've put up actual power figures, not like a lot of people here who take the rear wheel figure and then add on a percentage they feel comfortable with, sometimes up to 20%, to come up with a BHP figure



To the OP, you really haven't told us anything... do you have a website or a pic of anything? I would love a new intake pipe and a few extra ponies.
Plus you're one of the few tuners I've seen in this part of the world

 

Since the steering wheel is reversed, just wondering if the HP numbers are reversed too. (261.6 HP) LOL. Sorry guys couldn't resist.

 

Yeah good point, i'd just assumed it was a 4.0, if it's a 3.2 then that's very impressive!

These guys are just down the road from me, i'll pop in for a visit this week.

 

Can't wait for your report!

Cheers,

Don

 

did they make a 3.2 sovereign ?

 

Donb you got it. It is a 4 litre quad cam V8 with 230,000ks, which we have owned for five years. Since we did a major service to it and now tuned it, the motor is so smooth.

As far as AFR's go, turbo cars AFR"s should be around 12 to 1 under load and 13 to 1 for normally aspirated. Most cars from factory run way too rich. We also use Apexi Super AFC's to trim AFR's if the car has an air flow meter.

As far as the power goes, I think it is about right, in fact very good. To compare I had a Lexus LS400 4 litre quad cam V8, which stock standard only made 108rwkw, we added a very quiet high flow exhaust with large straight through custom made mufflers, trimmed AFR's with S AFC, modified intake and it made 150rwkw. The Jag almost made this standard.

 

Still sounds a bit low to me?

I did a 200 cell cat with exhaust and induction kit on a 96 XK8 with 120K on the clock and managed 290 bhp at the flywheel..... The condition of the engine is an obvious factor?

I will ask the customer for a copy of the print out when I see him next

 

Don't know much about rwhp from na cars, but the red curve (original one) isn't a normal one to begin with, there was certainly an issue there which isn't releated to the a/f mixture. Somehow that issue isn't there in the after run (well only very slightly).

 

I will not deny I have not had much experience with reading dyno sheets, something which I want to rectify..... I am more of your typical Joe and just tell me the end figure lol

 

Is your XJR modified or standard ? I ask because the difference between the quoted numbers ( 276 KW ) to the rear wheel numbers ( 240 KW ) which I take were taken after the car had a few miles under its wheels is only 13% . If standard I am impressed. Johns car seems to have lost 25% after being modified ? surely the ZF gearbox cant be robbing that much more power than the Merc gearbox ? Because aside from the blower , the drive shafts and diff are identical , even the same ratios ! I understand no two cars will be identical , and there will be a degree of variance between them , but surely not a nearly 50% difference ?

 

It was also a hub dyno, not a rolling road. I would expect slightly lower readings from a rolling road because of the tyres and momentum etc, but also the dyno I used has been known to read a little high... but that's not really of concern to me, what's more important is that it's consistent, and I could compare with a lot of other cars that have been on the same dyno, and also I can compare if I ever do any mods, as the car is completely stock.

FWIW I've had my car on a rolling road, it was measured at 250hp lol...