|
spatz
Original Poster
553 posts
13 months
|
I have been reading a lot of different opinions on this. There is the word that the LS7 block cannot take the additional stress,
however I would be using a procharger and the question is if 700hp would be possible without losing reliability ?
My engine install has some nice space between the dry sump tank and engine and I think a charger of that kind could just fin in there.
|
|
|
UltimaCH
457 posts
16 months
|
|
|
spatz
Original Poster
553 posts
13 months
|
yes I have seen that but they change a lot of the engines internal, the question is if it is possible on a stock engine
|
|
|
UltimaCH
457 posts
16 months
|
Not being an engine specialist, I would be careful regarding compression ratios. The LS7 is marked at 11.0:1 which is pretty high to start with. A low boost may be OK.
|
|
|
Boosted LS1
11,541 posts
87 months
|
I wouldn't bother given that the pistons are cast eutectics. In otherwords hard and brittle plus the static compression is a trifle high. You could use something like 5 psi but if the GM ecu doesn't protect your engine properly the pistons will crack at the first hint of detonation. The liners can crack as well.
It would be better to fit some forged pistons with a lower c/r and go from there if you're planning to do it properly.
|
Advertisement
|
|
|
738 driver
518 posts
20 months
|
Pro-chargers are a great piece of kit Spatz, particularly with Ultima installations......CanAm Dave has shown the way with his superb SBC version.
Centrifugal compressors are the most suitable for Ultima's IMHO.
I'd agree with Boosted with regards to an LS7 conversion though, to use its full potential you would need to go with forged internals. If you did go this route 700hp would be a breeze with 'some' more left (so long as you spec the rest of your installation to suit).
LS3's for slightly higher boost or even LQ9 blocks if you are looking to frequently run double figure boost.
GM LSX Bowtie block's should only be required if you are attempting to enter orbit at some point!
|
|
|
spatz
Original Poster
553 posts
13 months
|
so bottom line is that LS7 engine is made to be a very performant naturally aspirated and without modifications as you mentioned not really suited to be blown. I will skip this idea then and if I ever see the need for more HP I rather take a cheaper engine and mod it so it is suited for the task ? The guy who did my air bxo is welding titanium centers to aluminim pistons and they get very good results, this is the technology http://www.mozzi-kolben.com/Mozzi%20Kolben/Mozzi_K...maybe if I ever feel to work on my engine I will look into that and blow it then with lower C/R pistons. I understand that the titanium internals will be ok with the additional load ?
|
|
|
RichardD
2,197 posts
72 months
|
spatz said: so bottom line is that LS7 engine is made to be a very performant naturally aspirated and without modifications as you mentioned
not really suited to be blown. I will skip this idea then and if I ever see the need for more HP I rather take a cheaper engine and mod
it so it is suited for the task ? Going on basic crate UK pricing, there is £5000 difference roughly from the LS7 to the LS9, leaving you just 50bhp short of your target. I'd guess the 7 would fetch a decent second hand price !?
|
|
|
Boosted LS1
11,541 posts
87 months
|
It's hard to lower the c/r on an ls7 below about 9:1 as the rod little end's pretty near the piston underside.
You could use an ls3 block but the liners are a bit on the short side but it could be sleeved with longer and stronger liners. A cheaper option though would be an ls3 block, less stroke and appx 416 ci. This way you could use more boost and a longer rod to keep the pistons further into the bores at bdc.
Whatever you build will be cheaper then an ls9 but that does have some very nice rods and pistons inside.
|
|
|
60mph
228 posts
12 months
|
When I skimmed my cylinder head on DB4GT cr was 11:1 . PANIC they only made 100 cars and a few extra 'heads . Simple answer = 2 x cylinder head gaskets . Ran perfectly .
I can't quite see the logic in reducing cr then supercharging to gain the extra BHP youv'e deliberately lost . No benefit in low down torque either .
Frank
|
|
|
738 driver
518 posts
20 months
|
Thats very true Frank but do you suffer insufficient low end torque in a N/A V8 Ultima. Can you really get all that low end torque down or would you settle for a little less low end + lots more mid-top end.
Hence why the centrifugal compressor is more suited IMO.
Approx 50% increase in HP @ 10psi should hardly be deemed a 'few' extra HP.
|
|
|
Boosted LS1
11,541 posts
87 months
|
60mph said: When I skimmed my cylinder head on DB4GT cr was 11:1 . PANIC they only made 100 cars and a few extra 'heads . Simple answer = 2 x cylinder head gaskets . Ran perfectly .
I can't quite see the logic in reducing cr then supercharging to gain the extra BHP youv'e deliberately lost . No benefit in low down torque either .
Frank It's about having a greater volume into which you can pack the fuel/air molecules before they have to rub shoulders with each other, which is when they get angry. A bit like me at an autosport show where everybody is squeezed in together. The bigger volume means more fuel means more torque before you detonate. as for the torque, that depends on when you cram in the extra fuel.
|
|
|
V8 Vum
617 posts
48 months
|
Yes Boosted, BUT you need be a bit more selective! Go to the Autosports show on PRESS/TRADE day and you won't mind being squeezed between models at all!  What have I said?    Keith
|
|
|
spatz
Original Poster
553 posts
13 months
|
ok can you blow the stock ls7 with 10 psi or not and get 20.000 miles out of it ? simple question ?
|
|
|
Gulf -LS2
1,279 posts
31 months
|
spatz said: ok can you blow the stock ls7 with 10 psi or not and get 20.000 miles out of it ? simple question ? no, is the simple answer Spatz. 5 or 6 psi would be ok imo.... one of the directors at ProCharger runs a standard LS7 powered Vette with 5.5 psi and it allegedly has 700 bhp and has now completed more than 30'000 miles with no problems. Look at ls1tech.com as lots of guys on there are running standard 7's with varing amounts of boost.
|
|
|
spatz
Original Poster
553 posts
13 months
|
this is more or less what I thought, so mild blow with this charger, simple setup some extra horses runnig a belt and a little tubing, thanks
|
|
|
Gulf -LS2
1,279 posts
31 months
|
the standard ProCharger brackets will not fit in a Ultima..... we have made our own if you are interested in doing the conversion?
|
|
|
738 driver
518 posts
20 months
|
You can Spatz but be very careful...............its not as simple as merely following a front engined example.
When we fit everything in one compartment (as in the Ultima) the whole operating environment changes.
To get the sort of results many claim you have to run a well sorted and very fine tune......consistently.
Heat, vibration/resonance etc,etc,etc can all contribute to seriously upsetting this super fine tune...Dont relax at the thought your engines sensors will always protect you at peak performance. They can, occasionally, get confused/upset by environmental influences.
Not trying to put you off at all Spatz but the 'simple fit' isnt actually that simple in an Ultima, considerably more than just a charger, belt and some tube.
Maybe have a good read up before committing, there's some very interesting info around.
Good Luck.
|
|
|
spatz
Original Poster
553 posts
13 months
|
if i put one in there then it has to go the left side of the engine, and I need to run it on the same belt as the alternator which should be no problem as the pulley that is driving the alternator pulley is really a big one. I see that the max rpm for a P1-SC is 62.000 rpm. the ratio is 4,10:1 so the the pulley cannot exceed 15.121 rpm. My alternator is limited to 18.000 rpm and I am very close to that spec with the alternator pulley. So the procharger pulley can be a little bigger than the altertnator pulley which is good. The question now is how to I limit the boost to 5,5 PSI, can I put a valve or do you limit the max revs to achieve that ?
|
|
|
738 driver
518 posts
20 months
|
With a larger pulley...........to avoid drive problems.
Overboost is managed by pressure relief.
|
|
