The V8 Owners Forum -

I bought my TVR Chimaera 450 4 years ago on ebay for a bargain £6050.





Did a bit of the turny stuff



Tried the ¼ mile and got hooked as you do



Soon got bored with only 270 bhp in 1060kg car. Started playing with the nitrous.





First ever run was 14 seconds NA, to low 13’s on Toyo R888s and down to 12.2 with a 60 shot of nitrous on day 2. A lot of messing about finally ran in the 11’s with a best of 11.6 @ 125.
Won Yorks Hotrod Challenge 2009



Got carried away and made schoolboy errors resulting in this



Got carried away again stripping the car down to discover this mess…





Repaired the chassis and painted with POR15



Currently in this state with new 3 way nitrons and uprated driveshafts.








After much deliberation I took the engine to Mike Johnson (Boosted LS) in Nottingham for the rebuild.
New ceramic coated forged pistons....



Big valve heads fitted with bronze guides, 3 angle seats and ported by Pete burgess




Bespoke cam from Kent, 238 inlet, 256 exhaust with a fair amount of nitrous in mind














The final clean, checks and assembly has been done ready for me to collect on Friday.
Bottom end sorted, cam timed in, heads and rocker gear fitted and pushrods adjusted.

Now i can get it home and hammer on the rest of the bits.

Good stuff. That TVR chassis looks pretty solid (apart from the side impact protection..!)

Look forward to seeing the results.

Chris.

Good pics!

I'm messing about with NOS on my stage III 4.6 lump in my Cob replica.
Well I would be if the weather was good enough!

Hope you don't mind me asking but what were the "school boy errors" that you made? (So hopefully I don't make them! )

sidecar wrote:Good pics!

I'm messing about with NOS on my stage III 4.6 lump in my Cob replica.
Well I would be if the weather was good enough!

Hope you don't mind me asking but what were the "school boy errors" that you made? (So hopefully I don't make them! )

There is more to consider and check when running nitrous as we all know what can happen if we dont prepare. Mixtures run weak, detonation dangers and high cylinder pressures ant temperatures can spell disaster.

My 4.6 ran upto (and more sometimes on a second stage) 150 shot with no retard in the ignition. This was with some help from a progressive controller, grade 8 ngks, and only ever on the drag strip.

I would say upto 100bhp then only a grade cooler in plugs, a healthy spark and maybe a couple of degrees retard is all thats required on a 4.6 v8.

Also check your fuel supply is sufficient for the engine under sustained full load + the added requirement from the nitous system.
Lots of advice can be had on the wizards of nos forum.

Good work there.
It looks like I got off lighter than you did with the TVR chassis eating worms. It's a bit of a shock seeing how much is missing after you've been using the car to go quickly isn't it?

Looking forward to seeing how the new engine performs.

Very nice. We dont do much with nitrous over here, but I like what you have done.

Thanks
The Wedge Shop

dbv8 wrote:

sidecar wrote:Good pics!

I'm messing about with NOS on my stage III 4.6 lump in my Cob replica.
Well I would be if the weather was good enough!

Hope you don't mind me asking but what were the "school boy errors" that you made? (So hopefully I don't make them! )

There is more to consider and check when running nitrous as we all know what can happen if we dont prepare. Mixtures run weak, detonation dangers and high cylinder pressures ant temperatures can spell disaster.

My 4.6 ran upto (and more sometimes on a second stage) 150 shot with no retard in the ignition. This was with some help from a progressive controller, grade 8 ngks, and only ever on the drag strip.

I would say upto 100bhp then only a grade cooler in plugs, a healthy spark and maybe a couple of degrees retard is all thats required on a 4.6 v8.

Also check your fuel supply is sufficient for the engine under sustained full load + the added requirement from the nitous system.
Lots of advice can be had on the wizards of nos forum.

Cheers for the reply.

My system is quite different to yours in that it is spraybar system running under my AFB carb, it's only a single stage jobbie too.

According to the gumph that came with the Holley kit and a calculator that I got off the web my system should be adding 100BHP at the moment. It does not quite feel that much to me. More messing about when the weather picks up is required

Hi Sidecar
if you are jetted for a 100 shot then that should give you a significant push. On our engines you should feel a boost in torque by 150 lb/ft right through the rev range pretty much from the point the system is activated.
I would guess you are running too rich a mixture. This is 99% the case as its safer for your engine but saps power. You can lean off the mix by trying a smaller fuel jet but keep checking the plugs for signs of a weak mix. Also, do you have a bottle gauge? I fitted a heater to my bottle and a pressure switch keeps the bottle at 950 psi which provides excellent results and more importantly keeps it consistant.
Heres a dyno pic of my car running once NA then twice with a 75 shot.

dbv8 wrote:Hi Sidecar
if you are jetted for a 100 shot then that should give you a significant push. On our engines you should feel a boost in torque by 150 lb/ft right through the rev range pretty much from the point the system is activated.
I would guess you are running too rich a mixture. This is 99% the case as its safer for your engine but saps power. You can lean off the mix by trying a smaller fuel jet but keep checking the plugs for signs of a weak mix. Also, do you have a bottle gauge? I fitted a heater to my bottle and a pressure switch keeps the bottle at 950 psi which provides excellent results and more importantly keeps it consistant.
Heres a dyno pic of my car running once NA then twice with a 75 shot.

Very useful stuff!

Some details of my setup:-

Bottle pressure= 600 PSI. I can't get the pressure anywhere near the recommended 900 PSI. I don't have a heater but I did leave the bottle in the airing cupboard near the hot water tank for two days! (The pressure only went up to 650 PSI) I've decided just to jet the system for this pressure by using bigger NOS jets and then watch out for any increase in pressure in the summer.


Jets= 45 NOS, 44 fuel. I've not tested this setup yet but I did run 45/47 whilst monitoring the AFR using my Innovate LC1. It was rich with this setup at around 10-10.5:1

I now run an Edelbrock fuel pump that supplies both the carb and the NOS system. The pressure is 7.5 PSI. The fuel flow figure escapes me at the moment but I know that it was shed loads! (I use a formula help work out what's required. BHP = (Fuel flow per minute in CC) / 4.6

I run a Summit RPM duel window switch for the NOS system, once armed it comes in at 2700 RPM and off at 5500 RPM. I run a low fuel pressure cut off and a WOT switch.

I don't have an ignition retard but I'm thinking of making something using a solenoid the move the dizzy vac advance plate backwards. (I don't use the vac system, it's locked at the moment) 12 static, 32 all in at 2750-3000 RPM). I wasn't going to retard the ignition for any safety reasons, I've read that it is required because the burn rate is higher when NOS is being injected. (Maybe the high burn rate is due to the higher cylinder pressure before the fresh charge is burnt).


My engine is a stage III 4.6 running an RPI/Piper Stealth max 285 cam, Eddy Performer manifold matched to the V8 Dev heads, Eddy 500 carb (homemade rods and secondary jets). Vernier timing gear, adjustable pushrods, 1+3/4" primaries. 10:1 CR.

It puts out 285 BHP at 5500 RPM and around 300ftlbs. It's in a Cob replica that is hopefully under 1000Kgs.

Don't get me wrong, it goes go quite well when the NOS is running, maybe I was expecting my eye balls to pop out which hasn't happened!

(Maybe the high burn rate is due to the higher cylinder pressure before the fresh charge is burnt).

The high burn rate is due to the nitrous burning quicker than the air fuel mix. So the bang happens faster. We retard the ign timing so the faster bang can happen a bit later in the cycle to make more use of the big push from the explosion. If you have too much advance the explosion can try to slow the piston down on its way up which sends cylinder pressures through the roof. I think some of the pro boys running huge amounts of nitrous run ign timing at around 16 ATDC for peak power.

You would be better off getting a bottle heater so you dont have to guess at jets sizing in different weather conditions.

Is yours the normal spray bar plate with 2 bars on on of thoise crossbar plates?

I'm using a 150hp spray bar plate as my 2nd stage on top of my 1st stage fogger plate. It wont hurt to run more retard while testing as its the safest way to do it.
Are you using a high power ingnition system??

Perry

mgbv8 wrote:(Maybe the high burn rate is due to the higher cylinder pressure before the fresh charge is burnt).

The high burn rate is due to the nitrous burning quicker than the air fuel mix. So the bang happens faster. We retard the ign timing so the faster bang can happen a bit later in the cycle to make more use of the big push from the explosion. If you have too much advance the explosion can try to slow the piston down on its way up which sends cylinder pressures through the roof. I think some of the pro boys running huge amounts of nitrous run ign timing at around 16 ATDC for peak power.

You would be better off getting a bottle heater so you dont have to guess at jets sizing in different weather conditions.

Is yours the normal spray bar plate with 2 bars on on of thoise crossbar plates?

I'm using a 150hp spray bar plate as my 2nd stage on top of my 1st stage fogger plate. It wont hurt to run more retard while testing as its the safest way to do it.
Are you using a high power ingnition system??

Perry

Hi Perry,

I have thought about a heater but I've blown a fair bit of dosh on this system so I might have to save up my pennies first. The other thing is just how hot does the bottle have to get before the PSI gets up to 900? (To me it seems it is going to have to get bloody hot which means a shed load of current drawn from the battery!...and for how long?)

The plate under my carb has two spray bars in line with each other, one on top of the other. Is that good or bad?

The manifold is a 180 jobbie, the spray bars line up with the splitter. There is an open bore 8mm carb insulation plate between the manifold and the NOS plate.

My ignition system is just a 35DML8 with the amp on the side. I've done a few things to it such as lock the vac system because it does not work too well with the Eddy carb unless you run a really low static figure. I run more static than Rover recommend, 12 static 32 all in. I've reduced the plug gap down to 25 thou in the hope of not losing sparks when the NOS is running.

I've also modified the rotor arm to sort out a mis-alignment problem. (Not pointing directly at the HT posts when the system fires).

I'm getting more convinced that a 'retard when the NOS is running' system would be a good thing to make.

The car is only used on the road, the NOS system it's just something that I wanted to fit for the OTT factor!


Cheers,

Pete

Starting to make me think what my 4.6 is going to produce. especially with my gas kit capable of running 500hp

Must remember to get some processed cheese to check my piston to head clearances

sidecar wrote:

mgbv8 wrote:(Maybe the high burn rate is due to the higher cylinder pressure before the fresh charge is burnt).

The high burn rate is due to the nitrous burning quicker than the air fuel mix. So the bang happens faster. We retard the ign timing so the faster bang can happen a bit later in the cycle to make more use of the big push from the explosion. If you have too much advance the explosion can try to slow the piston down on its way up which sends cylinder pressures through the roof. I think some of the pro boys running huge amounts of nitrous run ign timing at around 16 ATDC for peak power.

You would be better off getting a bottle heater so you dont have to guess at jets sizing in different weather conditions.

Is yours the normal spray bar plate with 2 bars on on of those crossbar plates?

I'm using a 150hp spray bar plate as my 2nd stage on top of my 1st stage fogger plate. It wont hurt to run more retard while testing as its the safest way to do it.
Are you using a high power ingnition system??

Perry

Hi Perry,

I have thought about a heater but I've blown a fair bit of dosh on this system so I might have to save up my pennies first. The other thing is just how hot does the bottle have to get before the PSI gets up to 900? (To me it seems it is going to have to get bloody hot which means a shed load of current drawn from the battery!...and for how long?)

The plate under my carb has two spray bars in line with each other, one on top of the other. Is that good or bad?

The manifold is a 180 jobbie, the spray bars line up with the splitter. There is an open bore 8mm carb insulation plate between the manifold and the NOS plate.

My ignition system is just a 35DML8 with the amp on the side. I've done a few things to it such as lock the vac system because it does not work too well with the Eddy carb unless you run a really low static figure. I run more static than Rover recommend, 12 static 32 all in. I've reduced the plug gap down to 25 thou in the hope of not losing sparks when the NOS is running.

I've also modified the rotor arm to sort out a mis-alignment problem. (Not pointing directly at the HT posts when the system fires).

I'm getting more convinced that a 'retard when the NOS is running' system would be a good thing to make.

The car is only used on the road, the NOS system it's just something that I wanted to fit for the OTT factor!


Cheers,

Pete

Pete!!
Does your dissy send a signal to a normal coil??
I know zilch about these amplifier dissys so I assume its some sort of electronic trigger mechanism that gets its signal amplified to send a pulse to a dissy via a solid state relay?
If so I dont see why you could not fit an MSD coil for a better spark?

The amount of ign retard will vary between same type engines for peak power. The rule of thumb is 2 degree's of retard per 50hp shot of gas.

If you dont want to fit a bottle heater then you could always use some other method of heating the bottle before you try a run on the strip. You wil have to PM me for that info though
The bottle does not have to get very hot for the pressure to rise....
A fairly normal 250 watt bottle heater will drag about 20 amps when its on.

Heres a table of bottle temp vs pressure !!

http://www.nitroussupply.com/bottletemp.php

Your twin spray bar plate is the best for your type of manifiold as it will share its charge between the two plenums. There is a better option but its more dosh. And as you only want to use a small shot it should be fine.

Closing the plug gaps a little is a good idea if running a stock ignition system.

The main thing to check is that your fuel system can keep up with the demand + about a 50% safety margin !!

So for a 150 shot you would be hoping to have excess fuel supply of about 900 ml's per minute. 100ml of fuel per 100hp per 10 seconds is what you want to aim for.

The simple way to set your nos timing is just run the motor to 3000 rpm or whatever rpm see's max advance and move the dissy until you get the retard you need at max advance, which is where you need the retard. You may get a lumpy idle but you can just adjust the idle speed if she plays up at tickover. You can adjust this at the track for the odd day out.

Now the other info!!!

I have run my 3500 to a 100 shot with no retard. I have accidentally run my 4.6 to a 275 shot with no retard many times.

I have run my 4.6 to 10.6 seconds on gas with 4 degree's of retard and also with no retard??

But with no nretard I cracked a few pistons after about 15 passes. So I fitted Omega forged pistons and I can still run the 10's with a 275 shot on no retard??

I have now made a 2 stage nitrous system that will give me 300hp on stage 1. And another 150hp on stage 2. So I will be going back to basics and running a shed load of retard for my first test runs of 2011

You need to get yourself and your car down to the Pod for one of our days out so we can tune this thing for you mate

Hi Perry,

Thanks for the detailed reply, good info in there!

The dizzy just runs an amp which powers a bog stock coil. I was not sure whether these fancy coils are just snake oil or not.

I did measure the free flow of my fuel pump, the figure escapes me at the mo but it was something like 3 litres per minute. The low fuel pressure NOS cut off is set to about 7 PSI and it has never shut the system down so I'm sure that the fuel pump is up to the job.

Cracking pistons does not sound like fun, mine are only stock jobbies, they are also fly cut which I've heard can weaken them a bit too.

The pressure verse temperature chart is interesting, so you guys run your bottles at around 30 degrees C

Maybe come the summer I'll go for a blast down the Pod, the only problem is that my car is quite light at the back end, it lights the wheels up in second gear to the point of it being annoying!

Cheers,

Pete

sidecar wrote:Hi Perry,

Thanks for the detailed reply, good info in there!

The dizzy just runs an amp which powers a bog stock coil. I was not sure whether these fancy coils are just snake oil or not.

I did measure the free flow of my fuel pump, the figure escapes me at the mo but it was something like 3 litres per minute. The low fuel pressure NOS cut off is set to about 7 PSI and it has never shut the system down so I'm sure that the fuel pump is up to the job.

Cracking pistons does not sound like fun, mine are only stock jobbies, they are also fly cut which I've heard can weaken them a bit too.

The pressure verse temperature chart is interesting, so you guys run your bottles at around 30 degrees C

Maybe come the summer I'll go for a blast down the Pod, the only problem is that my car is quite light at the back end, it lights the wheels up in second gear to the point of it being annoying!

Cheers,

Pete

Pete!
The free flow of your pump is not what you need to measure for accurate testing.
Your 3 litres per minute is enough to run about 500hp. But you need to know what the pump will deliver with the resistance of the fuel system taken into account ?
I use a simple, but very crude method of doing this. And its not going to be a fave with the HSE guys
I'll come back to that via pm if you want more info !!
Are you happy that your pressure switch works at the set value?? Have you tested it ??
The MSD Blaster coils are good value items that deliver a good punchy spark for not a lot of money. I will leave it to the RV 8 experts on here to say if your module will trigger this ok. I assume it will though

You will only crack pistons if you run too much gas with too much advance. What is your RV8 engine size??

The nitrous bottles get fairly warm to the touch at 900 psi... And when doing as quick warm up with my (other method of warming the bottle) they can creep to 1200 psi quickly when full

My MGB GT does not have a lot of weight over the rear end. So I use slicks to get my traction. What car do you drive, and what rear tyres do you have??

And do you have LSD or a diff locker of some sort??

Perry