Safe Nitrous Boost

[800jer]

Hi. I have a Jaguar XJR X350 2004 that I have modded slightly for a few extra bhp. So far I have put a smaller pulley on the supercharger, had a remap, fitted sports cats and free flow exhaust system. I had her dyno'd a couple of weeks ago at 441bhp (fly wheel). Jaguar quote the car as 400bhp as standard but as for all manufacturers they are probably a little colourful with their figures and probably nearer 390 bhp. Any way the engine is a 4.2 litre V8 and at the moment for track use (drag 1/4 mile) I run a boost of 125bhp nitrous and with a charge boost from temperature drop in the supercharger probably giving an extra 20/25bhp. So all in all on full tap I am getting circa 585bhp. What would you guys recommend as a safe shot of nitrous for my car and engine as I would like to push the 600bhp mark and hopefully obtain between 600 and 650bhp ?

 

[old-git]

Hi

There is no way that we can suggest a safe nitrous boost for your engine as there are so many variables. Any one suggesting a figure is risking an engine failure. 125 is a pretty good shot already.

I suggest that you talk to your nitrous kit supplier as they will have a much better idea. However, even they will be cautious. In the end it will be your decision as to how far to push it Maybe up the shot in 25bhp increments, but be prepared for tears at some point as power is infectious

 

[800jer]

My initial setting was 100bhp and the car ran very nicely with that so I increased to 125bhp and the car still seems happy I think another 25bhp boost to 150bhp might be ok too as fuel supply from the two pumps seems quite adequate at the moment but I don't want to push things too much and end up with a bucket full of pistons and other bits and pieces.

 

[old-git]

Exactly why no one can acurately predict the safe limit. The only way to find this is to go one jet size too big It depends on how serious you are on getting to 650bhp and are you prepared to take the risks involoved? Only you can decide that.

What system are you using?

 

[800jer]

I have a Nytrex wet system installed. with a 10lb bottle

 

[old-git]

Where did you get it from?

 

[800jer]

I got my kit from Nimbus Motor Sports

 

[old-git]

How about talking to them?

 

[800jer]

Will do. I will wait until Im back in the UK next week.

 

[old-git]

Let us know what they recommend

 

[TCJBOLDIE]

Are they legal over there as it is illegal to even have the lines fitted without the bottle fitted/connected on a road car??

 

[800jer]

I have emailed them to see what they suggest. As for the legality of Nitrous then the answer is yes as long as your insurer is informed. I do not use mine on the road, only for days at the drag strip. So technically all I'm doing is carrying some extra pipes around in the car and it's not modified until I fit the bottle at the track side. I bet the insurers would argue different just to get some extra ££££s out of me though.

 

[TCJBOLDIE]

I gather from what you posted that it is a road car so technically it is "modified"as it didn't have the NOS plumbing fitted at the factory or as a listed option.

Sorry to be pedantic about details

My car is a road registered car and the following advise? is for people with modified cars

I have a highly modified car with all the mods"blue plated" = engineer checked and approved and a "blue plate with his details,date & mod type fixed in the engine bay.

Mods/changes that don't require engineer approval have also been passed on to my insurer and my insurer has them all listed on the policy.

Would advise you keep all correspondence on a file just in case.

IF your road car insurers have not been told of the NOS system or any mod whatsoever then it may give them an out in the event of a crash and you will have to repair whatever damage you cause to others as well as your own car.

 

[old-git]

Agreed. However, I am going to have to discuss this with my insurer as it will be very difficult to list every mod. Hopefully, we can come to an agreement so that there is no getout clause because I forgot to mention a fuse box.

 

[TCJBOLDIE]

Agreed. However, I am going to have to discuss this with my insurer as it will be very difficult to list every mod. Hopefully, we can come to an agreement so that there is no getout clause because I forgot to mention a fuse box.

Steve just give them the link to this thread

 

[800jer]

My insurer knows about the other mods on the car and was quite keen to bump up my premium when they heard about the supercharger upgrade and remap but they were not concerned about the exhaust. Like I said before the nos is only for track days and is never coupled up/Installed on the public road and as Insurance is only for the public road they can whistle.

 

[SLEEPER]

Sorry to sound harsh but it really isn't a question of the insurance company being keen to raise the premium - what do you expect ? it's their business Speed = risk = premium.

Anything as obvious as nos you really should tell them about . If you don't there was no point in telling them about any mod. You won't get 90% of any claim cos you told them 90% of the mods.
remember they will be even more keen to wash their hands if the worst happens ( it's what they do ) and it may not even be your fault.

As to the tuning .
Nobody can tell you the safe power limit for sure. Problem is ,as you've obviously found , power in itself is addictive
.
Just another 25 bhp bang! ............. Been there done it as have many .
The phrase occupational hazard comes to mind.
Seriously good luck and I hope you can control the addiction better than I can.

 

[lostviking]

There is only one way to answer that question. What is the peak cylinder pressure before damage? What shot keeps you below that level? You need to do some math.

It won't be a HP number, it will be pressure/volume of NOS.