I've made a few tweaks to the car recently and had the car retuned at RPM in DE. I had them do a baseline but unfortunately the information wasn't usable since the car was "spinning its *** off on the dyno". Perhaps it was strapped down loosely but they were confident they had enough tricks to make it hook up when they did the final tune.


While I was surprised peak RWHP nudged only slightly on the top end, midrange power and torque saw a very significant jump. Peak torque is up almost 50 from the previous trip to the dyno. While I would have liked to see those peak numbers rise for internet fame, I think the gains will make a significant difference on the track with a car as heavy as this. The A/F is much improved over the last tune as well which is nice.


RPM believes the LT1 ported intake may be the restriction. They don't think its the heads (LE TFS 208cc 21 deg units) since they flow comparable to a good set of ported LS1 units. They even pulled the air filter off the inlet to the head unit to see what would happen and it lost power. Go figure. I will probably ask Lloyd Elliot his thoughts since he would have a better handle on the power capability of my top end.


Since boost is beyond the capabilities of the MAF, the car was tuned in SD. Throttle response is much improved and overall driveability is just better in general. I think the MAF tune could have used some tweaking but the car drove fine, now it just drives more like a "normal" car. Acceleration is quick and smooth and the transition to PE is pretty seamless. I got stuck in a 2+ mile stop and go traffic jam on the NJ Tpk coming home with it yesterday from DE and I could putter away from 1k rpms in gear without any fuss. So far, I'm a fan of SD tuning and RPM did a great job taking care of the car. I'm pretty neurotic with it so leaving it in with anyone besides me just messes with my head.


New Numbers


SAE - 697.55 RWHP / 651.27 RWTQ
Uncorrected - 710.34 RWHP / 661.82 RWTQ


Tweaks from original setup:
- 3.5" Twin Procharger intercooler to 31x12x4 FMIC
- Single to Dual meth nozzle setup
- Smaller supercharger pulley
- Revised supercharger inlet

 

Sweet man. You're almost at 20psi? Runnin meth on that beast yet? SD is the way to go, never been a fan of the MAF.

 

Thanks Silas. Right about 19psi of boost now and yes I've been running meth since the start. I'm actually thinking my cam could be the restriction up top. It's pretty mild but I don't see it necessary to make a change at this point. I love the way it drives.

 

Great build man and great numbers but I have a few questions as I'm building a twin turbo LT1 I have a new Z06 maf I want to use but I see you're running speed density what are the advantages and disadvantages? Don't you have to run the injectors in batchfire mode and doesn't that use more gas then sequential mode? Also where do you have your water/meth nozzles installed and which system would you reccommend Snow, Coolingmist or ????? Finally what size injectors and fuel lines are you running and how much timing are you running initial and under full boost? Thanks for any help you can provide.

 

Blackbird how much timing are they running at WOT? If I remember right your tune at the timing around 17 degrees (they were raping the PE table as well)? They are thinking about LSX engines, Id run that thing around 28 wot timing.

I do a lot of tunes nowadays, SD is ok but it takes the IAT into it fueling calculations too much IMO. I usually do large housing MAF tunes to stay under the Hz limit and scale it to stay under the g/sec limit.

 

nice to see some lt1 love still around! were doing a very slow build on my buddys lt1, 383 with a bw s480. cant wait till the end of summer to see what she will do.

 

Thanks for the compliments. You can do a bunch of reading on it but the consensus from most of the well respected guys is that either can perform well if tuned properly. The MAF makes things more forgiving but again, if tuned right, neither will make more or less power. I have the EFI connection 24x LS PCM conversion system so I wouldn't be able to answer your batchfire mode questions. I have the meth nozzles mounted about 4 inches from the TB with the IAT in between. I went with the Snow stage 2 kit. Many swear by Alkycontrol but the Snow has been working fine for me since I installed it a few years ago. I am running 80lb Siemens HI injectors, stock fuel rails and lines. Double pumper from Lonnies in the tank and his wiring harness. I did not get a look at the tuning file but I will be requesting it just to have it.

I would have to get that info. I discussed this with them when going over the results and they know the LT1's take more timing than the LS cars. I had a large MAF housing but it was maxed out from 6000 to 6500rpm on the previous tune. It would have been worse with the additional CFM. So far, I'm liking the SD tune quite a bit but I'm not looking to claim one way being better than the other.

Some would call it love, others just stubborn.

Sounds like a fun build. Post the results when you get it done.

 

Thanks Blackbird I also have the 24x setup with the LSx pcm and I'm running twin Comp Turbo 6767s with billet compressor wheels and Jardine stainless turbo headers. I will be removing my fuel bucket and sending it to Lonnie's for dual pumps and wiring upgrade as well and getting the water/meth kit. T/A Kid will the Z06 maf work or do I need something bigger to run the maf and if so can you give me a reccomendation?

 

The Z06 is a 85mm unit, if your making any power with that turbo you will exceed the Hz limit due to the size of the MAF. A larger tube will lower the Hz range. For instance with a 4inch tube I have seen around 800 to the ground before it hits the 12,200 limit in the 24x computers (411), However the tune needs to be scaled, which means fuel and air needs to be scaled by the same percent. So a 50% scaled tune would exceed the limit of 512 g/sec of airflow to 1024 g/sec. That much airflow will give up to around 1000-1100 rwhp, all under MAF control. Also the Spark tables are extended past 1.36 g/cyl to 2.72 g/cyl, you don't get this with SD, you hit the last cell in the spark table and its used from there on out.

Both can be used just find, I just tend to use MAF.

Blackbird if you have access to your tune take a look at the spark tables. Im willing to bet you have some power left on the table.

 

I'd love to see your car man... jesus! that thing is sweet

 

I asked for the tune file just to have it and will let you know. I don't doubt there is more in the setup but I don't want the car tuned on the ragged edge. When I use the car, I'm pretty hard on it and its gone through a couple track rentals with the engine holding up without a problem.

I frequent NJFBOA often and there is a meet in May coming up. If the weather is good, I will have the Bird. Come on by with yours.

 

From what I've read, if you are running alot of boost with a MAF you will eventually max out the air flow tables. After they are maxed the computer cannot tell how much more air is going into the engine.

With a speed density tune is calculates the airflow differently and the scaling at higher flows isnt a problem.

 

Will do! I haven't been on there in a while.

I have been chasing a wicked vibration in my car... If it's fixed by then I'll be comfortable to drive it over an hour to that meet in Wall.