[Timbo-1LE]

New tune came with rev limiter set 500 higher, caught me by surprise as the new intake and tune, it just keeps pulling.

Any builders with real experience in this, have HP tuners and created a lower verion...

Thoughts?

Thanks

[Timbo-1LE]

Thx, motor is perfect condition. So you run it to 7k?

[Timbo-1LE]

Also an M6 car, it surprised me how it just pulled, before you could feel it and yank the lever when the COPD set in

[khcoaching]

Originally Posted by Timbo-1LE

New tune came with rev limiter set 500 higher, caught me by surprise as the new intake and tune, it just keeps pulling.

Any builders with real experience in this, have HP tuners and created a lower verion...

Thoughts?

Thanks

Curious as to what intake an tune?

[Timbo-1LE]

LT2 and Pray... I'm not questioning his expertise. Just caught me off guard and have a note into him. Daytona Friday night so simply checking. Note, check his Facebook page, while he did mine and it pulls hard all the way, not sure he believes this is a good investment over MSD, after I read it I understand why... Also, but 3.5 seconds off my best at Sebring on Saturday, it hauls the mail and recommend him highly. Which for those that know 3.5 seconds in a 3.7 mile road course with 17 turns is amazing..

[s346k]

my bolt on car has seen 7k+ quite a bit. you'll be fine.

[khcoaching]

Originally Posted by Timbo-1LE

LT2 and Pray... I'm not questioning his expertise. Just caught me off guard and have a note into him. Daytona Friday night so simply checking. Note, check his Facebook page, while he did mine and it pulls hard all the way, not sure he believes this is a good investment over MSD, after I read it I understand why... Also, but 3.5 seconds off my best at Sebring on Saturday, it hauls the mail and recommend him highly. Which for those that know 3.5 seconds in a 3.7 mile road course with 17 turns is amazing..

Thx! Exactly why I am asking....road course high RPM, for sure we are lacking the over 5500 rpm free rev and it's what I want to improve.

Ken

[JitteryJoe]

Everything I've read has said that sustained high RPMs are way worse than a short spike. Some cars (Lotus Elise) came with a variable limit that would let you overrev for a bit but then cut out if you stayed there too long.

[cmitchell17]

For what it's worth the GMPP LT1 LT535 crate motor, which is just a LT1 with cnc posted heads and the GM hot cam which I believe uses stock LT1 springs and "LS7" type lifters. The tune file for it is set at 7100 rpm extreme cutoff.

[Timbo-1LE]

Thanks cmichtell17... I have that cam sitting in a box in my office...

[cmitchell17]

Originally Posted by Timbo-1LE

Thanks cmichtell17... I have that cam sitting in a box in my office...

I should also mention how lean their AFR is:


You can see above 5600 rpms they are above 1.05 EQ ratio, which is around 13.43:1 AFR. Now I think they happen to find peak power at this relatively lean AFR. I know a lot of people will freak out when they see this, but given that this engine is direct injected I don't see how the fuel has almost any potential to cool the intake valve or any other component.

I mean that is the whole point of direct injection is that the fuel is vaporized mainly by the heat in the air charge in the cylinder and not the intake valve. So the heat gets pulled out of the air charge instead of going into the intake valve then to the oil and coolant. This then gives you cooler air charge that is more dense and should improve volumetric efficiency.

My TSP ported heads and cam LT1 spit out the intake valve seats. I was running E85 almost 100% of the time and I was using GMPP's EQ ratio table. A lot of people who I trust, including my machine shop and some other people pointed my failure to the tune being off. I still trust them but I don't believe this was why my intake valve seats starting pitting and breaking up. I think a lot of people are quick to blame tuning. The GMPPs tune EQ ratio however is very lean even for a NA direct injected application.

So I guess what I am trying to say here is maybe this supposed GMPP tune file is wrong, or maybe something was wrong with the flash (that's highly unlikely) or maybe whoever posted the GMPP file thought it was GMPP's tune file but maybe it was someone else who didn't really know what they were doing.

Or maybe it is in fact GMPP's file and we are safe to rev stock engines to 7100 rpms and run NA LT1s well above 13:1 and be ok?

[KingLT1]

While there are plenty of reports of factory castings having valve seat issues, you definitely were not doing yourself any favors running that lean.

There is no reason to run a engine that lean DI or not. Max torque is always found around 12.6:1. GM targets this AFR on the Stock SS file. You can gain a few HP running up around 13:1 but any leaner is just creating higher cylinder temps and heat.

I also do not see 7100rpm being a issue. LS stuff has been revving like that for years and the bottom end in the LT1 is actually designed better then the LS stuff.

Hell I target around .84-.85 Lambda on my brothers Gen2 383 LT1 running on E90. It's a 13:1 solid roller engine with 30 degrees of overlap. It pulls 1.0gr cylinder airmass according to the log so it's making some decent power. I would rather run a little fat on a performance engine that is going to see a lot of WOT pulls opposed to running it lean. You are only talking a few HP difference either way.

[Tim M]

Reference the rpm limit - I wouldn't feel comfortable exceeding 6800 or so on road courses. GM's valve spring are for longevity and mileage with a 6600 rpm cut. Even 300 rpm over will reduce the life (until when?) especially with those heavy DOD lifters.

A top speed run on mine brought it to a solid 6550 and not a mph more. I lean toward a valve train issue limiting as it was so abrupt (not exactly the same as yours as with a supercharger and BTR springs, but those same dang lifters...)

[Timbo-1LE]

Thanks. When I do the LT1 hot cam, it will be done by a shop with experience, so they can refine the tune from there. Just the new tune and LT2 pulled really nice at Daytona last night.