Doing my research, advice and thoughts wanted

Only by sending the ECU to Bywater or someone similarly qualified for remapping. Or ditching the OEM EFI for Megasquirt or the like so you can do your own fuel mapping.

1 Like

Hi

I have just added Nos to my pre HE V12 cobra to give up to 300bhp extra at the touch of a button

haven’t tested it yet though

peter

1 Like

That should fly like a pop bottle rocket!

…with report.

:grimacing:

1 Like

Will the rest of the drive train take that kind or torque?

Paul

Hi Paul

I’ve uprated the GM400 with Transgo clutches and a 35 element sprag and B&M quick shift

I have also installed a nitrous controller so I can program progressive nos injection

I will start small with an extra 30bhp and progresses upwards from there see how the car performs

Peter

1 Like

Sounds like something out of Mad Max!

The old rule of thumb is never to add NOS to provide more than 50% additional power without rebuilding and upgrading the bottom end. I think even 50% might be pushing it for the Jag V12. Have you done any strengthening down under?

1 Like

Hi Kirbert
I have rebuilt the engine with all new big ends piston rings etc but have not upgraded the bottom end yet for stronger parts, but agree 150 additional bhp would probably be the absolute maximum I would set the controller and jets to before fortifying the engine, the system does use a progressive controller and I have installed a vary speed race fuel pump. Have you seen the you tube video ?, (Boosting The Jaguar XJS with Nitrous Oxide) Top Gear.Wizard of nos used 200bhp increase on a standard XJS

Peter

Hi Kirbert

I have rebuilt the engine with all new big ends piston rings etc but have not upgraded the bottom end yet for stronger parts, but agree 150 additional bhp would probably be the absolute maximum I would set the controller and jets to before fortifying the engine, the system does use a progressive controller and I have installed a vary speed race fuel pump. Have you seen the you tube video ?, (Boosting The Jaguar XJS with Nitrous Oxide) Top Gear.Wizard of nos used 200bhp increase on a standard XJS

Peter

Why is there two identical posts, from two discrete member names?

Hi Wiggles

I used a different computer and logged in with an older user name that was stored peter-brown2
I have tried to delete this user name but have been unsuccessful
So I re logged on using my recent user name and re posted
Peter

1 Like

Years ago we had reports of someone’s highly-modified XJ-S – I think it was white with ground effects trim, and I think it once belonged to someone famous – that was equipped with NOS. It apparently blew up several times until the owner gave up and dumped the car.

Hi Kirbert
I found this report I think from your book
NITROUS: Martin R. Fooks has a nitrous system in his XJ-S: "The Nitrous system was supplied by Trevor Langfield and is a customized “High Power Nitrous” system. Because of the size of the hit to the engine (150BHP) they installed a progressive controller, which fits neatly in my car where the trip computer used to be. This enables me to control the way the extra power is delivered to the engine, such as starting power, ending power, time delay and time from starting level to ending level.

"I am very happy with the Nitrous installation, which really seems to be very smooth on the V12. Trevor’s people have the computer equipment to work out power and 0-60MPH times and that is where the figures came from. As a side note, it ran 5.3 seconds 0-60 with a standard TH400 and only 75BHP jets in the NOS system instead of the 150 jets.

“Nitrous got a very bad press in the past, caused mostly by people adding too much power to their engines, or by not richening the fuel mixture when the NOS was injected. The casualties in my case have been the torque converter and the rear IRS mounts, which were all bar 1 ripped off.” (See the notes regarding rear suspension mount weakness.)

"The engine is stock except for the exhaust and intake, and I have had no problems at all with it (unlike the torque converter).

"The builders of my system told me that they do not recommend putting any more than 50-75BHP into your engine without using a progressive system as avoidable damage to the engine could result.

“Their main concerns with adding 150BHP were not with the engine as they believe it to be a very strong and reliable item. The standard transmission and torque converter were their main objection to the increase which as it turns out was well founded.”

“The amount of power provided in total by the NOS system can be changed by installing new jets at an English price of 7 pounds per pair, so if 150BHP proves too much to handle, you can always fit a smaller pair taking very little time and expense. 200BHP is the maximum obtainable by my kit. My suppliers stated to me that as a rule they do not fit systems with more than 50% of the original engine power (which is why I’m only using 150 Jets instead of 200). Obviously this is not the case if you bullet-proof your engine.”

“This is similar to my system so I will limit the power increase at the moment to 150bhp and revs to 6500rpm the torque converter may be ok as the car is very light 1010 Kg”
Peter

K, have got 850HP with a std. bottom end. Everyone forgets these were designed as a RACE Engine with 4 bolt mains, then detune for street use.

Norman how did you get 850hp? Turbocharged?

6.8L. NA with 4V heads

1 Like

I’m guessing revved pretty high. IOW, you stress the bottom end with RPM but not with chamber pressures. If nitrous is applied, the bottom end will be stressed with chamber pressures. I dunno if that makes any difference, but it might. There’s also the question of what happens to combustion chamber temps and whether that might threaten the OEM pistons, but I really have no idea what nitrous does to combustion chamber temps.

Picked up a copy of “TWR and Jaguar’s XJS.” Looks pretty interesting!

More oxygen/more fuel = higher temps.

Yeah, see, that sounds like a formula for melted pistons to me, unless the bottom end has been rebuilt using some non-stock pistons.