Some LT1 Myths/Misconceptions
07-07-2003 | 04:16 AM
#46
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From: Buffalo, New York
Let me wade in a bit on the brake thing. If you took a set of stock rotors and cut slots or drilled them, it's hard to any gain. More likely there would be some loss of breaking efficeincy. NBut I doubt if anyone has done anything rigorous enough to put the ths issue to rest. The question that's harder to answer is "are there advantages to slotted/drilled rotors when properly designed and manfacured.
IOW: does it uprise anyone that a set of new slotted and drilled $1,000 Bear rotors works better than a set of stockers with 30,00miles on 'em? No one that I know who is reliable has answered the tough questions comparing apple-to-apples.
Take 4 sets of new rotors. Stock OEM, OEM drilled and slotted, Stock aftermarket wiht no slots/rotors, and modified aftermarket with slots and holes. Test all 4 against each in a variety of conditions. Make test of each combo using different pads.
Likely results.
1. Stock rotors/stock pads: best for street type use. Low wear, short, quiet stops with little brake dust,
2. Stock aftermarket rotor with OEM pads: very similar to #1 with a bit shrter stopping and a bit more fade resistance.
3. Stock rotors with upgraded pads v. aftermarket stock rotors with upgraded pads. Both improve over stock/stock bit aftermarkat imprived more.
4. Drilled and slotted OEM rotors with OEM pads would be the worst of the bunch. OTOH, the drilled and slotted OEM parts with good pads are likely to be the best of the OEM variations.
5. The full on aftermarket set of drilled/slotted rotors and premium pads will probably be the best of the bunch.
But it the comparison of the drilled/slotted version of the OEM and aftermarket rotors that sheds the most light on what works and why. Seems to me that you would degrade the perfromance of OEM rotors and pads by messing with the rotor. OTOH, if you had a rotor and pad designed to work as a drilled/slotted system you would have a good performing systedm.
The final conclusion would be that a properly designed and manufactured drilled/slotted rotor wiht properly selected pad is more effectrive than an OEM system. And that drilling and cutting slots on stock rotor/pads degrades the performance.
Just my $0.02
Rich Krause
IOW: does it uprise anyone that a set of new slotted and drilled $1,000 Bear rotors works better than a set of stockers with 30,00miles on 'em? No one that I know who is reliable has answered the tough questions comparing apple-to-apples.
Take 4 sets of new rotors. Stock OEM, OEM drilled and slotted, Stock aftermarket wiht no slots/rotors, and modified aftermarket with slots and holes. Test all 4 against each in a variety of conditions. Make test of each combo using different pads.
Likely results.
1. Stock rotors/stock pads: best for street type use. Low wear, short, quiet stops with little brake dust,
2. Stock aftermarket rotor with OEM pads: very similar to #1 with a bit shrter stopping and a bit more fade resistance.
3. Stock rotors with upgraded pads v. aftermarket stock rotors with upgraded pads. Both improve over stock/stock bit aftermarkat imprived more.
4. Drilled and slotted OEM rotors with OEM pads would be the worst of the bunch. OTOH, the drilled and slotted OEM parts with good pads are likely to be the best of the OEM variations.
5. The full on aftermarket set of drilled/slotted rotors and premium pads will probably be the best of the bunch.
But it the comparison of the drilled/slotted version of the OEM and aftermarket rotors that sheds the most light on what works and why. Seems to me that you would degrade the perfromance of OEM rotors and pads by messing with the rotor. OTOH, if you had a rotor and pad designed to work as a drilled/slotted system you would have a good performing systedm.
The final conclusion would be that a properly designed and manufactured drilled/slotted rotor wiht properly selected pad is more effectrive than an OEM system. And that drilling and cutting slots on stock rotor/pads degrades the performance.
Just my $0.02
Rich Krause
07-07-2003 | 09:20 AM
#47
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From: looking for a flow bench so Brook and I can race
Originally posted by brand-x
I've been reading the slotted rotor -vs- regular rotors and I second what I read above.... The misconception as I understand it is (scary thought), the slots or drilled holes are less about cooling and more about relieving pneumatic gas buildups under the pads that prevents the pad from making full contact with the surface of the rotor--they prevent the traditional cause for brake fade.
I've been reading the slotted rotor -vs- regular rotors and I second what I read above.... The misconception as I understand it is (scary thought), the slots or drilled holes are less about cooling and more about relieving pneumatic gas buildups under the pads that prevents the pad from making full contact with the surface of the rotor--they prevent the traditional cause for brake fade.
07-07-2003 | 09:40 AM
#48
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Joined: Jan 1999
Posts: 835
From: Paris, Texas
Okay... I have to jump in on the brake issue.
There is NO performance gain with modern pads when using slotted or drilled rotors. Modern pads do not build gas like the pads from many years back.
Slots were added to sweep the pads clean of old pad material and the drilled holes were added to releive the gas pressure build up. Niether of which are necessary today.
Also under heavy brake use... the drilled rotors will NOT last long. Cracks will form around the holes.
Someone always brings up Porsche rotors.... They are CAST holes and not drilled holes thus less prone to cracks. But most still believe they are for the bling bling.
I open track road race my car and have gone through my share of brakes and see alot of different brake setups.
Different brake pads will make a difference in braking ability, but not just adding slotted/drilled rotors.
There is NO performance gain with modern pads when using slotted or drilled rotors. Modern pads do not build gas like the pads from many years back.
Slots were added to sweep the pads clean of old pad material and the drilled holes were added to releive the gas pressure build up. Niether of which are necessary today.
Also under heavy brake use... the drilled rotors will NOT last long. Cracks will form around the holes.
Someone always brings up Porsche rotors.... They are CAST holes and not drilled holes thus less prone to cracks. But most still believe they are for the bling bling.
I open track road race my car and have gone through my share of brakes and see alot of different brake setups.
Different brake pads will make a difference in braking ability, but not just adding slotted/drilled rotors.
07-07-2003 | 09:51 AM
#49
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Joined: Aug 2001
Posts: 3,505
From: looking for a flow bench so Brook and I can race
Originally posted by All_Z_Way
Okay... I have to jump in on the brake issue.
There is NO performance gain with modern pads when using slotted or drilled rotors. Modern pads do not build gas like the pads from many years back.
Slots were added to sweep the pads clean of old pad material and the drilled holes were added to releive the gas pressure build up. Niether of which are necessary today.
Also under heavy brake use... the drilled rotors will NOT last long. Cracks will form around the holes.
Someone always brings up Porsche rotors.... They are CAST holes and not drilled holes thus less prone to cracks. But most still believe they are for the bling bling.
I open track road race my car and have gone through my share of brakes and see alot of different brake setups.
Different brake pads will make a difference in braking ability, but not just adding slotted/drilled rotors.
Okay... I have to jump in on the brake issue.
There is NO performance gain with modern pads when using slotted or drilled rotors. Modern pads do not build gas like the pads from many years back.
Slots were added to sweep the pads clean of old pad material and the drilled holes were added to releive the gas pressure build up. Niether of which are necessary today.
Also under heavy brake use... the drilled rotors will NOT last long. Cracks will form around the holes.
Someone always brings up Porsche rotors.... They are CAST holes and not drilled holes thus less prone to cracks. But most still believe they are for the bling bling.
I open track road race my car and have gone through my share of brakes and see alot of different brake setups.
Different brake pads will make a difference in braking ability, but not just adding slotted/drilled rotors.
with the rotor spinning so fast- i find it hard to believe that air can actually make it through the holes..
07-07-2003 | 11:54 AM
#50
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Joined: Apr 2003
Posts: 121
From: South Carolina
Re: Re: Some LT1 Myths/Misconceptions
Originally posted by Dan K
I'd like to see some of the more knowledgable ECM guys here get together and write a really short tuning page or slap a sticky at the top of the computer/diagnostics page (and lock it) as a basis to start tuning an LT1 from. Should help those just getting started quite a bit.
I'd like to see some of the more knowledgable ECM guys here get together and write a really short tuning page or slap a sticky at the top of the computer/diagnostics page (and lock it) as a basis to start tuning an LT1 from. Should help those just getting started quite a bit.
07-07-2003 | 12:08 PM
#51
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Originally posted by FlyBono24
Camaro Performers magazine just ran an article about the Baer slotted rotors on 3rd Gen's, and they had a noticeable difference in stopping...
Camaro Performers magazine just ran an article about the Baer slotted rotors on 3rd Gen's, and they had a noticeable difference in stopping...
You will burn in hell for that one.
-Mindgame
07-07-2003 | 12:14 PM
#52
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Posts: 2,325
From: BC
Originally posted by treyZ28
porsche does a lot of stuff other than cast holes- i beleive they cast soduim or soemthing like that in the actual rotors as well...
with the rotor spinning so fast- i find it hard to believe that air can actually make it through the holes..
porsche does a lot of stuff other than cast holes- i beleive they cast soduim or soemthing like that in the actual rotors as well...
with the rotor spinning so fast- i find it hard to believe that air can actually make it through the holes..
07-07-2003 | 12:21 PM
#53
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Joined: Aug 2002
Posts: 470
From: Detroit, MI
!spare tire
can someone please explain to me why people do this, these cars are already too heavy on the front and too light on the back so why would you pull out the spare, i see this as one of the better design Q's GM made (putting it on the right), its weight along with a relocated battery may help with traction and pull down those 60' times a notch?
07-07-2003 | 04:29 PM
#55
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Joined: Jun 2002
Posts: 2,456
From: sarasota, fl
Re: !spare tire
Originally posted by chevyboy_z28
can someone please explain to me why people do this, these cars are already too heavy on the front and too light on the back so why would you pull out the spare, i see this as one of the better design Q's GM made (putting it on the right), its weight along with a relocated battery may help with traction and pull down those 60' times a notch?
can someone please explain to me why people do this, these cars are already too heavy on the front and too light on the back so why would you pull out the spare, i see this as one of the better design Q's GM made (putting it on the right), its weight along with a relocated battery may help with traction and pull down those 60' times a notch?
07-07-2003 | 04:34 PM
#56
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Posts: 10,745
From: Buffalo, New York
This thread is getting long! Did someone already mention another LT1 myth? The larger throttle body for a stock or near stock car? That's another myth, which I have personally seen debunked on the dyno. FWIW, the "RamJet 502" I recently looked at appears to use a twin 48mm throttle body (like a stock LT1), though I didn't measure.
Rich Krause
Rich Krause
07-07-2003 | 05:12 PM
#57
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Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
Misconceptions...
1) That, out of a listing of cams with similar specs, the cam with more lift is always going to make more power than a cam with less.
2) That the 7k rpm shutoff is easily achievable with camshaft duration in the 230-ish range on 350 ci motors.
3) That a cam with 240-ish duration is not "streetable" in a stroker.
4) That things are black and white and what works for one combination will work exactly the same for another.
5) That solid roller cams are "high maintenance".
6) That there are not trade-offs when looking for horsepower.
I'll think of more later.
-Mindgame
1) That, out of a listing of cams with similar specs, the cam with more lift is always going to make more power than a cam with less.
2) That the 7k rpm shutoff is easily achievable with camshaft duration in the 230-ish range on 350 ci motors.
3) That a cam with 240-ish duration is not "streetable" in a stroker.
4) That things are black and white and what works for one combination will work exactly the same for another.
5) That solid roller cams are "high maintenance".
6) That there are not trade-offs when looking for horsepower.
I'll think of more later.
-Mindgame
07-07-2003 | 05:43 PM
#58
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Joined: Jan 2002
Posts: 616
From: West Palm Beach, FL
Originally posted by JSK333
FWIW, about the '93s and FP... they will adjust to changes just like '94+ because the PCM operates the same way (anything that brings the car away from 14.7:1 AFR will cause the BLMs to "fix" it). It has nothing to do with the MAF sensor, which is why '93s are affected too.
FWIW, about the '93s and FP... they will adjust to changes just like '94+ because the PCM operates the same way (anything that brings the car away from 14.7:1 AFR will cause the BLMs to "fix" it). It has nothing to do with the MAF sensor, which is why '93s are affected too.
right or wrong? Anyone with a 93 and AFPR?
07-07-2003 | 05:45 PM
#59
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Joined: Jan 2002
Posts: 275
From: Goose Creek, SC
Re: Some LT1 Myths/Misconceptions
Originally posted by rskrause
I was thinking about this for some reason. Here's some myths and misconceptions FYI.
As with plugs and wires, coils and ignition boxes are also pointless mods for stock or near stock car. The OEM pieces are quite up to the job of efficiently igniting the mixture and there are no gains to be had replacing them unless they are malfunctioning.
Another concerns changing the fuel pressure. The stock tune for an LT1 is a little rich, so leaning it out with an AFPR will add a few hp. But the change won't last, due to the ability of the PCM to learn. No, the PCM does not directly sense FP. But over time will compensate for a lean condition and bring the mixture right back to where it was. You can still use the AFPR to improve track performance by clearing the PCM before each run. But you won't gain anything messing with the FP in a typical street situation.
A related myth is that there are gains from making timing changes. The stock timing is quite agressive and only works because the knock sensor function allows improper operation (low octane fuel, high load at low rpm, etc.) without damage. There will be no gain from advancing the timing on a stock or mildly modded vehcile running on pump fuel.
Rich Krause
I was thinking about this for some reason. Here's some myths and misconceptions FYI.
As with plugs and wires, coils and ignition boxes are also pointless mods for stock or near stock car. The OEM pieces are quite up to the job of efficiently igniting the mixture and there are no gains to be had replacing them unless they are malfunctioning.
Another concerns changing the fuel pressure. The stock tune for an LT1 is a little rich, so leaning it out with an AFPR will add a few hp. But the change won't last, due to the ability of the PCM to learn. No, the PCM does not directly sense FP. But over time will compensate for a lean condition and bring the mixture right back to where it was. You can still use the AFPR to improve track performance by clearing the PCM before each run. But you won't gain anything messing with the FP in a typical street situation.
A related myth is that there are gains from making timing changes. The stock timing is quite agressive and only works because the knock sensor function allows improper operation (low octane fuel, high load at low rpm, etc.) without damage. There will be no gain from advancing the timing on a stock or mildly modded vehcile running on pump fuel.
Rich Krause
, average 13.x go to www.ws6.com to see more details) do u think i'd see any kinda gains like that with the mods i have currently? And please be honest!! Also when i have my LT1 edit done will the comp. after a while reset itself from the programmed psi back to its factory setting?? I'd think that'd defeat the whole purpose of an edit but i thought i'd ask!Thanks Rich!
Last edited by CamaroRob97; 07-07-2003 at 05:49 PM.
07-07-2003 | 06:00 PM
#60
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Joined: Jul 2001
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From: so close I can taste it...
Re: Re: Some LT1 Myths/Misconceptions
Originally posted by CamaroRob97
Now i've been told by a good friend that LT1s (like u said) run a tad bit high on psi, if i get like the LG Motorsports fuel pressure regululator that on a dyno proved 16.x HP ( , average 13.x go to www.ws6.com to see more details) do u think i'd see any kinda gains like that with the mods i have currently? And please be honest!! Also when i have my LT1 edit done will the comp. after a while reset itself from the programmed psi back to its factory setting?? I'd think that'd defeat the whole purpose of an edit but i thought i'd ask!
Thanks Rich!
Now i've been told by a good friend that LT1s (like u said) run a tad bit high on psi, if i get like the LG Motorsports fuel pressure regululator that on a dyno proved 16.x HP (
, average 13.x go to www.ws6.com to see more details) do u think i'd see any kinda gains like that with the mods i have currently? And please be honest!! Also when i have my LT1 edit done will the comp. after a while reset itself from the programmed psi back to its factory setting?? I'd think that'd defeat the whole purpose of an edit but i thought i'd ask!Thanks Rich!
If you read that website more, you'll see that those gains were quickly negated as the computer adjusted injector pulsewidth to correct for the fuel pressure adjustment.
Second, nothing that the computer does can change your actual fuel pressure. What it will do is correct for the lean or rich condition that you created by changing your fuel pressure with the regulator. It will do this with injector pulsewidths.
Third, I have heard that on 93's the computer doesn't correct for fuel pressure changes in the same way the later LT1's do. But I have no first hand proof of this as the only 93 that I've done we set the fuel pressure to 43psi and I changed the fueling in the computer by modifying the VE tables and pe tables.
Hope this helps.