JjCoDeX75

Not an actual project for me, just a hypothetical question....

Could you get 500 bhp from a std comp cossie, and if so, how would you do it?

Dont want to get too tied up in the std comp vs low comp thing though.

Thoughts.....

JJ

BigErn

Mines standard comp, supply all the parts for me and Ill give it a go.

Chip

iTrader: (3)

You do it by making boost at higher RPM, so that you dont end up with the timing too retarded.

Trouble is, the heads are a bit asthmatic for that unless heavily worked, and it means missing out on some of the midrange torque you would have at lower CR as you will have to cap the boost at lower rpm.

GARETH T

i think you could make 500bhp, not just on standard compression, but on a totally standard engine

it wouldnt be ideal though

Chip

iTrader: (3)

Head is the part of the standard engine that would give you the most problems trying to get 500bhp IMHO, but I agree that I dont think it would stop you if a 500bhp figure is your only concern, it would just probably end up slower in most real world situations than a well specced 450bhp motor with far more torque!

cossiemanden

I`ve seen a few sweedish engines with little over and under 500brake on an std bottom, BUT head had to be ported tho.
Worked fine, was REALLY fast and quick on boost also

Stavros

RS500 sorta spec with race fuel would manage it on 8:1 or maybe more.

Pump fuel is a bit harder tho, wilder cams, mentaller heads, bigger turbos, basically so you can get the power from revs rather than mega boost.

GARETH T

i believe you could take a totally stardard engine,, gt40 or something,, and 500 bhp would be smashed

Deleted by Request

...guys you forget surge if using a std head...been there done that virtually!

You'd need a T4 minimum (and tbh youd need 2.5bar plus LOL) to make the 500bhp and at over 1.5bar you cannot get thru the surge (and my head was mildly ported)...roller bearing turbos would be even worse!.....I spose you could use a complicated jap boost controller though till 6k revs to cap the boost and then wack her up to around 2.5bar to get 500bhp maybe at 7.5K RPM?..Not sure though as std ports have real trouble accepting that amount of air.

A std engine will make 400bhp max IMO.

Stavros

you mean in your mind, claiming stuff on the net with no proof whatsoever?

Deleted by Request

..ask Steve Scott you clueless moron he set the car up and diagnosed it...Stavros please do not tar me with you.

Chip

iTrader: (3)

Phil, you dont need 2.5 bar of boost to see 500bhp on a cossie engine, you could see it at under 2 bar easily if it was at 9000rpm


Loads of ways of skinning that cat, not just the way you happen to have tried and failed to do it.



Gareth, I agree, if you strap a big enough blower on (with a massive hotside housing thats laggy as hell and doesnt spool up early enough to have problems with surge) 500bhp on totally standard engine has got to be a breeze, it just wouldnt drive very nicely!

GARETH T

and thats why i said "it wouldnt be ideal though"

Chip

iTrader: (3)

If you fancy doing it as a project, I have a spare engine (the one in my car I couldnt give a flying fuck about its only a temporary one anyway) and turbo (gt42r) that is suitable, but I dont have a manifold
Im sure we could get doug to knock something up though

Deleted by Request

Chip a std engine wont take 9000rpm not on std lifters so although you may get a flash 500bhp figure it would drop the valves..if they dont hit the pistons first and bend em thru over revving ..Then that is assuming the std head gasket dont blow,the 205 block dont crack,the head dont go thru your windscreen .....crank and rods will be fine though

...i would have thought there was more intelligence from you technical wannabes

Chip

iTrader: (3)

Phil, where has anyone suggested 9K on standard lifters?

My point about lots of revs was just to try and educate you that big boost isnt the only way, it wasnt my suggestion of what we would do with a std engine if we gave it a go, anyone with half a brain could see that!


Behave like a grown up phil, or at least go and try and start an argument elsewhere.

ECU Monitor Enthusiast

iTrader: (1)

Some interesting views on this thread

Deleted by Request

...you really ought to change that pedantic attitude ...you think get a std engine put a gt42 on and voila......you may get 500bhp on 1bar from it but the volume of air is still the same as a t4 at 2.5bar or whatever what boost that needs to acheive it on a std engine...and to put in simple terms for you chip..the head cannot accept that amount of air flow .....you have a lot to learn it appears

Stavros

if the head cant accept that amount of air phil, how would it only read 1bar and not still 2.5?

pressure is a measure of restriction

Chip

iTrader: (3)

Phil, if there was only 1bar of boost in the manifold that means that the engine is happily swallowing all the air flowed by the turbo, if it wasnt there would be 4 bar in the manifold instead.

You really havent got a CLUE about what "boost" actually is do you Phil?

Its a measure of restriction as much as it is of turbo flow.

Stavros

Just said that

Basically,you know it, i know it, phil dont know it...

He hasnt a clue

Chip

iTrader: (3)

Sorry mate, your reply wasnt there when I opened up the thread, apologies for repeating you, especially as its going to do no good to try and get phil to understand anyway

ECU Monitor Enthusiast

iTrader: (1)

Phil,

Stavros and Chip are quite right....



Now that made me piss my pants

JjCoDeX75

Okay, forgive my dullness, but I wont learn if I dont ask!

How does the compression ratio affect the power directly then? I know that it somehow relates to advance of the ignition, but surely if the head cant flow the air for big boost on std comp, what changes for low comp?

Cheers guys

JJ

Deleted by Request

If you have a small turbo you're going to have to run a higher pressure ratio to get the same airflow as a larger unit

Don't Confuse Boost with Airflow!!!!!...its the airflow the cossie cant take hence why you open up the ports

JjCoDeX75

Fair enough, but doesnt answer the question.

Question still stands, but subsititute the word boost with airflow then

JJ

Deleted by Request

NOTHING....execpt you can run more advance the lower the comp.

JjCoDeX75

So how is it that you can achieve 500 bhp relatively simply in a low comp engine when compared to a std comp? Or am I underestimating the difficulty in a low comp engine.

JJ

Deleted by Request

...you can get 500bhp 0n low high or whatever......you just got more issues with det on the std comp due to less advance...but 500bhp is easily within the std comps capability plus it should make more power at lower boost.

Deleted by Request

...the thread has gone all cold


...remember a T4 at 1bar will make more power than a T34 at 1bar..why?...MORE AIRFLOW...and if we dont open the ports we get SURGE past a certain pressure...so strap a GT42 on and it should spin up at around 5.5k i reckon 1bar from that is equivilant to 2bar airflow on a T4 ...so surge city on std ports...learn from me folk..i wont blind you with big fancy words.

ECU Monitor Enthusiast

iTrader: (1)

Phil,

You are right about the surge issues but they can be managed with
the right set up using boost control as you said above.

The point of this thread was to see if it possible.

It is and I have seen it myself on an engine dyno.

It wont be nice to drive or the is right way to do things but it can be done.

Deleted by Request

...Simon i am just mythed by chip and stavros's limited knowledge on boost! ...to them 2bar is 2bar of airflow whatever turbo

ECU Monitor Enthusiast

iTrader: (1)

2 bar of airflow - Thats like saying 3 pints of ball bearings.

Stavros

Deleted by Request

JjCoDeX75

Hi guys

A lot of interesting discussion so far.

Before we go further, can I just make sure that I am clear - effectively the boost seen by the inlet depends on how much air can flow through both the engine and the turbo. If the turbo is small, then the pressure is effectively 'backed up', so volume is reduced, and the pressure is increased. This is why 2 bar in a T3 is different to 2 bar in a T4.

Have I got this right?

Okay, so lets say you are blueprinting an engine for 500bhp. This is the end goal. Lets bring low comp back into the equation now. I am really curious as to how one would go about doing it.

I happily admit to my own ignorance on the matter of compression ratio. I have only ever myself experienced std comp, so cant comment at all on low comp. The purpose of this hypothetical has changed ever so slightly now to make a good driving 500bhp engine!

Discuss.....

JJ

ECU Monitor Enthusiast

iTrader: (1)

JJ spot on

GARETH T

sounds good to me

in the second half of your question,, are you asking about how to make your engine a low compression engine?

JjCoDeX75

This makes sense now - and also makes other things make sense. I was having a chat with Stu the other day who was explaining to me that the best performance from the turbo was actually at the point when the wastegate begins to open.

I guess that at this point, we have a situation where the turbo is making peak boost, and the engine is allowed to flow maximum air. Cool - that actually makes sense now!

Credit also to Chip who explained it again on the phone to me today!

JJ

Deleted by Request

...with a T4 to get you 500bhp your not gonna be making full boost very early so you would want std comp to get the drivability before all hell breaks loose..i have had 7.1-1 and 7.9-1 on the same set up...to go std comp over low you would have to take extra precautions like use liners (personnal preference) ..wrc long stud and wrc head gasket a nessescity IMO.

To lower the comp youd buy low comp pistons barring in mind how much your head is skimmed into the equasion.