Stock Headbolts

[spuddy]

Right I'm fairly familare with the ins and outs of the potential of stock bolts but I'm after a little reassurance.

Firstly I'm assuming compression ration plays a big role in how much boost they can deal with.

My comp ration is 7.6:1, now I know they stock bolts will take 1.8 bar, even 2.2bar on my current turbo.

I'm planning ahead for next year, has anyone ever ran nitrous+high boost on stock bolts? If not, would a 50 or 100 shot of gas produce more or less strain than 0.4bar of boost on the head bolts?

In terms of replacing the headbolts with ARPs, I don't want to destroy a brand new Cruise HG, so can I remove 1 bolt at a time and instantly replace it with an arp bolt, so that the head is never removed and should remain torqued enough to prevent oil/coolent to seap out?

 

[gt 4efte]

The last part of youw post, is also mine question,
i don't wanna waste my new Zep 1,2mm metal gasket, to expensive.
but wanna go ARP bolts, can you do one by one? or will its gona leaking?

stefan

 

[-Harry-]

Its not so much how much boost it can take but more so how much power. like you mentioned CR plays a part and so can gas. I ran 300hp at on my old setup with 17psi boost and 75hp shot of gas with a cr of just over 9:1 when the head lifted.

As for changing bolts, do a search, it was pretty well covered a while back. Theoretically you should be fine doing it your way as the gasket shouldnt move. Personally I wouldnt but im a pussy and a A$220 gasket isnt worth the pain in the ass. In the thread a while ago, some of the malta guys said that you can do it no worries so Id take their word for it. Id find the thread to confirm that though before removing them

Hope that helps

Cheers

Harry

 

[spuddy]

Hi harry lad, I know you Aussie lads talk wheel horse power so I assume the 300 is whp.

My own setup will be 300whp before adding gas, but the comp ratio is alot lower than your setup. Would you think this would perhaps allow me to push to 320whp with the gas running?

Damn thats not much boost at all on your setup.

 

[dan_ep82]

Hi harry lad, I know you Aussie lads talk wheel horse power so I assume the 300 is whp.

My own setup will be 300whp before adding gas, but the comp ratio is alot lower than your setup. Would you think this would perhaps allow me to push to 320whp with the gas running?

Damn thats not much boost at all on your setup.

for the money why dont you just put ARP ones in?

 

[spuddy]

I will be, but would still like to know these things.

 

[dan_ep82]

well i think dave b had the same problem as above running 320bhp on his old 4e using a shot of nos the head lifted off, it seems the stock bolts are ok until around 2.2 bar maybe more untill nos is thrown in

 

[spuddy]

well i think dave b had the same problem as above running 320bhp on his old 4e using a shot of nos the head lifted off, it seems the stock bolts are ok until around 2.2 bar maybe more untill nos is thrown in

I'll have to give him a ring tomorrow.

I stumbled across this, dunno how accurate it is but damn the compression ratio with boost is very very high!

http://www.rbracing-rsr.com/compression.htm

 

[Fatman]

Wow.. 7.6:1 is very, very low.. what was the thinking behind that?

As Harry said, it's not about boost, it's about power. Boost on one turbo doesn't equate to the same on another. Torque to yield bolts are never going to be ideal for a very high powered setup, I think it's pretty much invevitable that they will fail on upwards of 300hp, might not be immediately but it will definitely happen.

 

[spuddy]

The low compression has always been in mind for high boost and nitrous, I understand the addition of gas vastly increases cylinder pressures.

I will eventually increase the comp ratio, but not until I decide to run a much higher octaine fuel.

Surely if you have 2 cars both running say 300hp, it can be achieved via a high compression build with low boost or a low compression build running alot of boost. I would imagine within the cylinder for both to produce 300hp they are both going to have the same cylinder pressures, only achieved in two very different ways.

Maybe I'm thinking of it wrong, the drinks in so I have a very experamental imaginative frame of mind

Also whats your opinoin on the head bolt replacement without destroying the HG?

 

[spuddy]

Ok my second question is.

Would running 1.5bar with a 50-100shot be much more rewarding on the 1/4mile than 1.8bar alone.

My setup is fairly laggy, the introduction of nitrous would spool my turbo much sooner and allow me to change gear around 6800rpm to keep the car in its optimum powerband rather than reving round to 7100rpm and thus quite a bit out of the efficent powerband of my setup, however I am aware than by adding gas, my powerband is prob going to change dramatically.

I'm thinking alot of these questions can't be answered, theres not alot of guys running gas on the 4E/5E engines in the UK.

 

[-Harry-]

Id reccommend the a small shot of gas with a bit less boost. You will notice a huge difference in response. Running a DYO class it can also just be used as a 'fuck up' button. For example, you miss a gear then you hit the gas for a second and your back where you would be. It cn also prove to be more inconsistant in DYO classes do to things like bottle pressure, wheelspin ect. If its outright speed then go the gas for more response. Youll probably find with a 100 shot your going to need to drop a heap of timing or boost to stop it pinging anyway. Depending on what ecu you run will depend whether you can have the activation of the kit pull the timing or whether you have to sacrifice the timing at all times across the map. You may also be able to setup activation per gear to help wheelspin. You may be better off with a 30-50hp shot to start with. Remember 'NOS' hp rating are general ratings and given as flywheel power. A 50 shot on my car gives me just over 20 peak hp but up to 80hp midrange.

Sounds like you have a competitive car though. Id leave it alone to rule out any unknown variables. Finish off the season then have a play.

 

[sx_turbo]

you can change the arp bolts 1 at a time.

and there is nothing wrong with your compression ratio for your size turbo and bost wanting to run etc etc etc.

my cr is 7.85:1 and i'm using 6cc sish pistons and 1.2mm headgasket, the guy who built my engine said this was pretty much spot on for the ammount od boost i want to run on my turbo td04, he also said in his opinion, low compression was needed, because the 4e is such a small engine and putting high boost through it would put a lot of strain on such small big ends and little ends. and i think he knows what he's on about as he used to builf ford wrc engines