[Jmcmanus626]

Question for all the engine modders out there. I finally got a 2017 2SS, and I'm looking to eventually supercharge and get more RWHP from my car. I know about swapping internals for forged and all that but my question really lies in fuel and the likes for such. I'm aiming to get around 850hp and was curious if 91 octane is still feasible for such a build and HP or if at that point switching to an e85 flex fuel kit would be the better route. Can the LT1 still run that high of HP on 91 or no? Apologies if this is posted on the wrong section. Any advice or help on this topic would be appreciated!

[Gunkk]

Originally Posted by Jmcmanus626

Question for all the engine modders out there. I finally got a 2017 2SS, and I'm looking to eventually supercharge and get more RWHP from my car. I know about swapping internals for forged and all that but my question really lies in fuel and the likes for such. I'm aiming to get around 850hp and was curious if 91 octane is still feasible for such a build and HP or if at that point switching to an e85 flex fuel kit would be the better route. Can the LT1 still run that high of HP on 91 or no? Apologies if this is posted on the wrong section. Any advice or help on this topic would be appreciated!

You came to the right place. There is much wisdom and lots of experience building LT1s for big power in this section.

You are correct to sort out fueling first for your power level.

Can the LT1 be made to run 850 on 91? What's that quote from Red October when the Alpha attack sub captain asks for 105% on the reactor ... "Possible, but not recommended." (you can guess how the story ends for them). tl/dr: no.

[arpad_m]

I say why tempt fate with crap gas, unless you can't get either 93 or E85 in Cleveland. If that's the case, however, I wouldn't even try to go up to 850 hp (assuming you meant rear wheel hp, not crank).

You didn't mention how you'll want to use the car, but I assure you that 850 rwhp, which is nearly 1000 crank hp, can't be put down to the ground at low speeds in a RWD car unless you go with crazy tires, at which point it's hardly a street car anymore... I mean, 60-130 or 60-150 rolls are nice, but I've been to Cleveland, you'll be in jail pretty soon if you try that on a regular basis. Even then, I only have 735 rwhp and tried things like the Toyo R888R, it didn't hook from a dig but already had serious disadvantages.

So, let us know your actual goals before taking recommendations, because that matters a lot.

[Jmcmanus626]

Originally Posted by Gunkk

You came to the right place. There is much wisdom and lots of experience building LT1s for big power in this section.

You are correct to sort out fueling first for your power level.

Can the LT1 be made to run 850 on 91? What's that quote from Red October when the Alpha attack sub captain asks for 105% on the reactor ... "Possible, but not recommended." (you can guess how the story ends for them). tl/dr: no.

I figured as much. I was searching everywhere online for answers but couldn't find anything directly related to the Gen V LT1. I figured I would need to make a swap to an E85 flex fuel kit, I just didn't want to commit to anything I can't go back on before getting all the information I could on this subject. Appreciate the reply!

[Jmcmanus626]

Originally Posted by arpad_m

I say why tempt fate with crap gas, unless you can't get either 93 or E85 in Cleveland. If that's the case, however, I wouldn't even try to go up to 850 hp (assuming you meant rear wheel hp, not crank).

You didn't mention how you'll want to use the car, but I assure you that 850 rwhp, which is nearly 1000 crank hp, can't be put down to the ground at low speeds in a RWD car unless you go with crazy tires, at which point it's hardly a street car anymore... I mean, 60-130 or 60-150 rolls are nice, but I've been to Cleveland, you'll be in jail pretty soon if you try that on a regular basis. Even then, I only have 735 rwhp and tried things like the Toyo R888R, it didn't hook from a dig but already had serious disadvantages.

So, let us know your actual goals before taking recommendations, because that matters a lot.

My goals are to have a nice dual purpose car. One I can take to the track, but also cruise around in. To be honest I'm just petty and hate mustangs and hellcat drivers and want a sleeper. As for the PD issue I ain't to worried given my daily occupation as one. I'm not looking to street race but looking to have a nice power house I can enjoy not only driving but taking to the drag as well along with car shows when they roll around.

93 is readily available around me (Westlake area) E85 is aswell but not nearly as available if that makes sense.

[2SS Capt]

Originally Posted by Jmcmanus626

My goals are to have a nice dual purpose car. One I can take to the track, but also cruise around in. To be honest I'm just petty and hate mustangs and hellcat drivers and want a sleeper. As for the PD issue I ain't to worried given my daily occupation as one. I'm not looking to street race but looking to have a nice power house I can enjoy not only driving but taking to the drag as well along with car shows when they roll around.

93 is readily available around me (Westlake area) E85 is aswell but not nearly as available if that makes sense.

I think if you aimed for 550-600 RWHP you'd be quite happy, have a very streetable "sleeper" and do everything you want to do without having to go crazy into the engine...

[arpad_m]

Originally Posted by Jmcmanus626

My goals are to have a nice dual purpose car. One I can take to the track, but also cruise around in. To be honest I'm just petty and hate mustangs and hellcat drivers and want a sleeper. As for the PD issue I ain't to worried given my daily occupation as one. I'm not looking to street race but looking to have a nice power house I can enjoy not only driving but taking to the drag as well along with car shows when they roll around.

93 is readily available around me (Westlake area) E85 is aswell but not nearly as available if that makes sense.

Great info, thanks, all makes sense. Hopefully others will chime in, too, because I don't have that much experience, all I'm saying is that low speed acceleration is going to be traction limited almost no matter what you do. E85 helps in every way, I use it whenever I can (not super available, but not unobtainium here either), because the engine runs better and cooler with it, but 93 is okay, at least up to a point. I think 850 rwhp is difficult (= expensive) to achieve on 93.

If you ever drove a ZL1, it's hard to achieve a much faster low end acceleration than that with this architecture unless you use drag tires, the extra hp and all the engine work helps the most past 100 mph. My car used to be pretty weak above 90 mph and it simply "slid off a cliff" on the 4-5 shift (110-112 mph), but now it feels like it's "coming into its element" at 100 and above. Theoretically speaking, of course.

Don't get me wrong, once the tires hook it's gonna pull like a freight train with that much power, but the more low end torque you add, the more difficult it is to launch the car, you can't even mash the throttle at lower speeds let alone from a dead stop.

Note that a centrifugal supercharger (Procharger) helps with this somewhat, because it has a much smaller low end torque "hit", building torque gradually like a turbo instead. My preference was a positive displacement supercharger where there is little torque variance across the rev range, because my thinking is once the tires hook, I want to be sure that I have traction at WOT no matter what---everyone's needs are different, that's why it's good to have options.

[Jmcmanus626]

Originally Posted by arpad_m

Great info, thanks, all makes sense. Hopefully others will chime in, too, because I don't have that much experience, all I'm saying is that low speed acceleration is going to be traction limited almost no matter what you do. E85 helps in every way, I use it whenever I can (not super available, but not unobtainium here either), because the engine runs better and cooler with it, but 93 is okay, at least up to a point. I think 850 rwhp is difficult (= expensive) to achieve on 93.

If you ever drove a ZL1, it's hard to achieve a much faster low end acceleration than that with this architecture unless you use drag tires, the extra hp and all the engine work helps the most past 100 mph. My car used to be pretty weak above 90 mph and it simply "slid off a cliff" on the 4-5 shift (110-112 mph), but now it feels like it's "coming into its element" at 100 and above. Theoretically speaking, of course.

Don't get me wrong, once the tires hook it's gonna pull like a freight train with that much power, but the more low end torque you add, the more difficult it is to launch the car, you can't even mash the throttle at lower speeds let alone from a dead stop.

Note that a centrifugal supercharger (Procharger) helps with this somewhat, because it has a much smaller low end torque "hit", building torque gradually like a turbo instead. My preference was a positive displacement supercharger where there is little torque variance across the rev range, because my thinking is once the tires hook, I want to be sure that I have traction at WOT no matter what---everyone's needs are different, that's why it's good to have options.

I appreciate all the info! It's been very helpful! I WISH I could have a ZL1 but that's forever out of my price range sadly, but building on my super sport over time is a much more feasible option hence why I started asking here for opinions on these things. Would love to drive one eventually but I'm very happy with the SS just like I said I'm petty and hate hellcat owners. Hahahah.

I'm definitely gonna start looking at some E85 flex fuel kits then so I can at least get some planning together for when I start building.

[Jmcmanus626]

Originally Posted by 2SS Capt

I think if you aimed for 550-600 RWHP you'd be quite happy, have a very streetable "sleeper" and do everything you want to do without having to go crazy into the engine...

Which all makes sense. I've just always wanted to build on and mod a Camaro, I've owned 3 since I was in high school just never was feasible then and I like having projects to kinda build and work on and learn about. But even then if I don't go to 850, I guess my question still remains, can I still run 91/93 on such? That's really what I'm asking about cause I cannot find anything concrete in terms of that answer in regards to my specific engine. I find a lot on LT1s but half the time they don't specify what generation of LT1.

[arpad_m]

What I heard from shops and tuners is that even 93 is barely good enough for ZL1 power levels, let alone several hundred more that you mentioned. Using 91 kind of defeats the purpose of a build, because spark timing has to be pulled back a lot just to avoid knock.

Don't forget that the LT1 has a higher compression ratio than the LT4 (11.5:1 vs 10:1), which means it's even more octane sensitive, unless you go into the engine and reduce the compression ratio.

[Jmcmanus626]

Originally Posted by arpad_m

What I heard from shops and tuners is that even 93 is barely good enough for ZL1 power levels, let alone several hundred more that you mentioned. Using 91 kind of defeats the purpose of a build, because spark timing has to be pulled back a lot just to avoid knock.

Don't forget that the LT1 has a higher compression ratio than the LT4 (11.5:1 vs 10:1), which means it's even more octane sensitive, unless you go into the engine and reduce the compression ratio.

Makes sense. Looks like E85 will be a move regardless of power I put into it just to save me any ass-ache later down the road. Appreciate all the info and input! 🙏🏻

[cjperformance]

E85 for sure. My build is basically E85, port inj, procharger. I did a 3k stall conv too, but wish i had stuck with a stock stall.

I estimate my power level to be high 600whp maybe as much as 700.

Even with DRs, on the street, 1st and 2nd gear are useless at wot, and theres no traction at wot until 35-40 mph. Plus on a wot downshift it can suddenly rip the tires loose even at 50/60 mph.

I think i was happiest at around 550-600 whp. Fun to drive at that level without the huge fear of breaking loose all the time.

I think you would only need to go higher if you are planning on wowing folks at the track. I ran 10.8@131 before I added port inj and smaller pulley. I should have just stopped there. More just doesnt add anything for a primarily street driven car for me.

[KingLT1]

91 isn't enough octane for the LT1 NA let alone adding boost. Have shops put superchargers on these engines with 91 for fuel...yes. But they don't run close to what the dyno numbers they get out of them show because you have to be very aggressive with timing retard in regard to air temp on the street. Those cooled down hero dyno pulls are about 75-100whp higher than what you will actually be getting on the street in the warmer months.

I would just do a LT4 fuel system, 7-8psi, and run E60. Make 600-620whp... Simple easy to tune setup without any additional complex fuel systems needed and plenty of fun for a streetcar. The Ethanol will allow you to maintain max timing even when it's hot which equals much more consistent power. If you want to push further than that for power, 700whp is about max I would push a stock bottom end LT1. Port Injection/Low side upgrade and 10-11psi will get you there. Or if you want to stay DI only for fuel then you will need +30 injectors, LPE HPFP, and JMS low side booster.

[FH212]

What about us people that the best gas we have available is 91 at our higher altitude? Are we just cursed?