Supercharging / Compression Ratio

[hsv_sc]

I've been looking at info on the CAPA website about supercharger setups for the LS1...

According to CAPA, with the LS1 you don't need to lower the compression when using a supercharger at 5 psi or a supercharger and intercooler combo when running more then 5 psi..

Can anyone confirm this or got more info?

[MadMaxHSV]

Commonly the compression ratio is lowered when FI is used as it allows you to run more boost and you easily make up the power lost from the lower ratio. It obviously adds cost (new pistons) or potentially loses reliabilty (thicker head gaskets). Not sure if the our engines run that high a comp ratio as standard so it may not be much of an issue. Times i've seen it done have been on standard 'relatively' stressed NA engines (ie. m3's) which run a high comp ratio to make their power.

[hsv_sc]

hmm.. have just checked and the standard CR for the LS1 is 10.1:1 according to a few websites.

clearly the LS1 can handle increased FI using the std CR... if it's good for CAPA it's good for me lol.

[crisisjez]

Almost without exception all the FI cars on here are running std compression.

[hsv_sc]

thanks jez, that's what i wanted to hear!

[EssexHSV]

If capa says its ok i just bolt it on.
All the guys at capa know there stuff so why not give them a call. Ive had a few things from them over the last 6 months and might be using them again soon.

[ringram]

My mate put a capa intercooled centrifugal on his SS VE Holden and got 340rwkw aka ~450rwhp.... until he wiped it into a fence

[V8HSV]

crisisjez said:

Almost without exception all the FI cars on here are running std compression.

I am running 8:1 with + 9 p.s.i. boost from a Vortech SC with forged internals.

Even with forged internals you can still have problems as I have new pistons on order with Roger due to no 3 cyc piston ring broken into many pieces through detonation, This is the 3rd time I have lost pistons, 2nd time requiring a new block, go anything over 5 or 6 p.s.i. and you might exoperience problems and have never been above 9 p.s.i. to date!

[V8HSV]

EssexHSV said:

If capa says its ok i just bolt it on.
All the guys at capa know there stuff so why not give them a call. Ive had a few things from them over the last 6 months and might be using them again soon.

A lot of additional parts on my car were CAPA, some now removed as they were never needed, from experience they liked to fk over their previous agent in the UK as they swapped my HSV ECU for a 17" wheel Commadore ECU a while ago, fitted a Gilmore SC drive from them with a pulley for 12 psi, it was no improvement on previous pulley producing 9 p.s.i. so I am not entirely happy with CAPA especially on 'what they say' although their product quality is 100%.

[hsv_sc]

V8HSV said:

crisisjez said:

Almost without exception all the FI cars on here are running std compression.

I am running 8:1 with + 9 p.s.i. boost from a Vortech SC with forged internals.

Even with forged internals you can still have problems as I have new pistons on order with Roger due to no 3 cyc piston ring broken into many pieces through detonation, This is the 3rd time I have lost pistons, 2nd time requiring a new block, go anything over 5 or 6 p.s.i. and you might exoperience problems and have never been above 9 p.s.i. to date!

sorry to hear of your troubles.. CAPA say they run their LS lumps with std CR and over 10psi with no det problems.

what ecu/management are you using now?
where do you get it mapped/setup?
is your Gilmore sc a centrifugal or roots, screw etc?

Edited by hsv_sc on Monday 11th August 12:12

[S600VXR]

Detonation is a tuning issue not a component issue, with good ECU programing you can get away with alot but as soon as your fuel map f**ks up the internal components will fail as yours have. I'd stop wasting money on stronger internals and start kicking arse over the fuel setups if I was you!! 12psi here, no detonation and (dare I say it!) no issues either in 17K! most of that in the hands of Brian who hardly drove it easy!

[ringram]

Yep tuning can help fix just about any compression issue. However it may be well away from MBT and far away from anything optimal as you may have to retard timing and overfuel it to get it to run safely with 50bhp, when it should be running 500bhp if it was setup properly. The basic mechanicals should obviously be made for a certain purpose or application. But the tuning will tie it all together as best as possible.

Scan tools good for giving your engine a "health check" and ensuring there is no knock, good fueling, no stored codes etc.

[crisisjez]

S600VXR said:

12psi here, no detonation and (dare I say it!) no issues either in 17K!

Yeah but you drive like a girl

[S600VXR]

176 vs 175...

You in the country BTW this weekend?

[crisisjez]

Gunna be at the pod on Sat.

Should be free sun.

Ahem....172.... Miss Daisy

Edited by crisisjez on Monday 11th August 13:39

[S600VXR]

crisisjez said:

Gunna be at the pod on Sat.

Should be free sun.

Ahem....172.... Miss Daisy

Edited by crisisjez on Monday 11th August 13:39

175 actually - last run and buried it in the red like you do in 5th! Would do the pod but have a buckled wheel awaiting replacement. BBQ Sunday if dry... will PM you unless your crying over a broken engine!

[crisisjez]

Exactly..172... untill the driving God showed you how
OOOOHHHHH free food... I`ll give you a call mate.

Edited by crisisjez on Monday 11th August 14:06

[stevieturbo]

V8HSV said:

crisisjez said:

Almost without exception all the FI cars on here are running std compression.

I am running 8:1 with + 9 p.s.i. boost from a Vortech SC with forged internals.

Even with forged internals you can still have problems as I have new pistons on order with Roger due to no 3 cyc piston ring broken into many pieces through detonation, This is the 3rd time I have lost pistons, 2nd time requiring a new block, go anything over 5 or 6 p.s.i. and you might exoperience problems and have never been above 9 p.s.i. to date!

Thats entirely down to tuning. Dont blame broken pistons or rings on faulty components.....It can hapen...but would be incredibly rare

Im around 9.0:1 and circa 20psi......Ive yet to have a failure, that wasnt my own fault with regards to detonation.
Not to mention head gaskets lol

[V8HSV]

stevieturbo said:

V8HSV said:

crisisjez said:

Almost without exception all the FI cars on here are running std compression.

I am running 8:1 with + 9 p.s.i. boost from a Vortech SC with forged internals.

Even with forged internals you can still have problems as I have new pistons on order with Roger due to no 3 cyc piston ring broken into many pieces through detonation, This is the 3rd time I have lost pistons, 2nd time requiring a new block, go anything over 5 or 6 p.s.i. and you might exoperience problems and have never been above 9 p.s.i. to date!

Thats entirely down to tuning. Dont blame broken pistons or rings on faulty components.....It can hapen...but would be incredibly rare

Im around 9.0:1 and circa 20psi......Ive yet to have a failure, that wasnt my own fault with regards to detonation.
Not to mention head gaskets lol

No need to lay blame with the person who set it up & tuned it (they know who they are) & fully realise the reason for PR failure was fuel starvation/detonation by way of the ECU's map. All I was stating is that forged internals does not make the engine bullet proof if its not set up right.

Edited by V8HSV on Monday 11th August 14:16

[V8HSV]

hsv_sc said:

V8HSV said:

crisisjez said:

Almost without exception all the FI cars on here are running std compression.

I am running 8:1 with + 9 p.s.i. boost from a Vortech SC with forged internals.

Even with forged internals you can still have problems as I have new pistons on order with Roger due to no 3 cyc piston ring broken into many pieces through detonation, This is the 3rd time I have lost pistons, 2nd time requiring a new block, go anything over 5 or 6 p.s.i. and you might exoperience problems and have never been above 9 p.s.i. to date!

sorry to hear of your troubles.. CAPA say they run their LS lumps with std CR and over 10psi with no det problems.

what ecu/management are you using now?
where do you get it mapped/setup?
is your Gilmore sc a centrifugal or roots, screw etc?

Edited by hsv_sc on Monday 11th August 12:12

The person who left their mark on the car initially took all guidance from CAPA, been tuned many times, now have had it wiped from the ECU with a new custom tune from Wortec whilst with Monkfish. The CAPA supplied kit featured a Vortech SC, so I guess thats a centrifugal type.

Pistons have arrived from the US (custome made) and hoping Roger can get them fitted soon.