Initial Tuning Steps Cadillac LH2 V8 Engine

[Bwnunnally]

I am starting to experiment with basic tuning for the LH2 V8 engine in my "new" 2007 XLR using data captured from hptuners and Brad Barnhill's Virtual Dyno. Unfortunately due to lack of a handy runway I am doing my Virtual Dyno runs in 2nd gear, so not directly comparable with a chassis dyno that is usually done in the gear closest to 1:1. Appears however to be fairly consistent and repeatable.

First, I wanted to adjust the tune to recognize that we have E10, or gas with up to 10% ethanol. This gas has a lower stoichemic makeup, and an ideal ratio is 14.2:1 air:fuel instead of non-alcoholic gas at 14.7:1 air:fuel. The Cadillac factory tune assumes 14.7:1 fuel. I set the tune to 14.4:1 since we have an uncertain mix of alcohol in the fuel.

[Short version: lost power, on to next test]

Read More:Initial Tuning Steps Cadillac LH2 V8 Engine

 

[GizmoQ]

I am starting to experiment with basic tuning for the LH2 V8 engine in my "new" 2007 XLR using data captured from hptuners and Brad Barnhill's Virtual Dyno. Unfortunately due to lack of a handy runway I am doing my Virtual Dyno runs in 2nd gear, so not directly comparable with a chassis dyno that is usually done in the gear closest to 1:1. Appears however to be fairly consistent and repeatable.

I've always liked your purely scientific analyses! Keep up the great blogging!

 

[Bwnunnally]

Thanks. It would be a lot easier with a huge garage and a chassis dyno.

I do like that I think most people have the ability to replicate the type of testing I am doing. New post for the Volant intake install & test is up.
Next I believe will be more baselines with the air intake, then experiments with LH2 VVT tuning since that would seem to give the greatest opportunity.
I also plan to get back to tests & tune for my STS-V LC3, but similar VVT tuning may help there as well.

 

[lextoy]

very interesting, lots of us here are looking for some power in the LH2, but since not much is available, its mostly got to be found in the tune.
i'll have to dredge up a thread i had about all the possibilities, see if any of it is useful for your endeavour.

update, heres my consolidated list on performance, not much to work with for you, but if you have a 2007 XLR
at least some of it might be of interest if you want to improve what little you can.
your tuning may be the only thing that gets any meaningful hp and torque...
https://www.xlr-net.com/forums/cadi...rmance-improvement.html?highlight=volant+gear

 

[lextoy]

so cool to read all your results and data on the XLR and other cadillacs.
a few laymans thoughts here, i am no where near as knowledgeable as you are!
seems like heat is a major factor for the LH2, i guess thats typical with all engine performance.
testing in texas doesnt help either, hahaha.
is your front rubber skirt(under the bumper) known as the valance, in good condition?
it helps with airflow into and out of the engine compartment, you probably understand this better than i do,
but its a part that is often overlooked as it is actually very difficult to see.
what about removing the engine cover to help reduce manifold temps? it looks purely cosmetic to me,
and your intake temps make sense but the manifold temps seem to get pretty high...
maybe thats the excessive ambient temps in texas, i am used to temps in the northeast,
everything runs cooler when its only 65 outside!
did the volant decrease temps significantly? mostly due to better flow,
i am sure, as it doesnt have a better "cold air" intake area than the stock setup.
any noticeable differences with top up or top down when measuring at the MAF
as far as pressure and how air flows thru and over the front of the car?
i know drag is higher with the top down, is engine performance effected as well?

 

[Bwnunnally]

so cool to read all your results and data on the XLR and other cadillacs.
a few laymans thoughts here, i am no where near as knowledgeable as you are!
seems like heat is a major factor for the LH2, i guess thats typical with all engine performance.
testing in texas doesnt help either, hahaha.
is your front rubber skirt(under the bumper) known as the valance, in good condition?
it helps with airflow into and out of the engine compartment, you probably understand this better than i do,
but its a part that is often overlooked as it is actually very difficult to see.
what about removing the engine cover to help reduce manifold temps? it looks purely cosmetic to me,
and your intake temps make sense but the manifold temps seem to get pretty high...
maybe thats the excessive ambient temps in texas, i am used to temps in the northeast,
everything runs cooler when its only 65 outside!
did the volant decrease temps significantly? mostly due to better flow,
i am sure, as it doesnt have a better "cold air" intake area than the stock setup.
any noticeable differences with top up or top down when measuring at the MAF
as far as pressure and how air flows thru and over the front of the car?
i know drag is higher with the top down, is engine performance effected as well?

Thanks for the link to the performance thread.

My undercar valance and skirting appear to be okay. With the air at 95F+ everything is going to be hotter than that cooling medium most of the time.

Interesting that the air in through the Volant actually showed 2F cooler than ambient (99F ambient, 97F IAT1) instead of 5F+ warmer than ambient with the OEM system. I would like to see more testing but my guess is the Volant does less unintentional pre-heating. Air in the OEM system has to go into the side-scoop, down through the filter, back to the middle, through the MAF, through the resonator, and into the throttle. The Volant eliminates some of that hot plastic.

Initially I tested with top down b/c I enjoy top down. Tests can be done either way as long as they are consistent. However, because the drag coefficient for the top down is another variable, I have been testing only with top up as a control. I suspect the top down adds ~0.05 to the CD. I believe top up/down would have marginal effect on air flow into the engine. That in itself would actually make an interesting series of tests. Within a range one could test top up x3, test down down x3, then modulate the CD in virtual dyno until the results overlapped. This would then reflect a measured CD more or less for top down.

I do test with A/C off and with transmission in TUTD. I have also not tested on/off to show what hp is lost to A/C on/off.

I have a tune 4 where I have done typical "turn up the advance 2 degrees" but I would like to get more baseline runs with Tune3 and the Volant first before we test Tune4.

The VVT tuning appears to follow conventional wisdom but I would like to try "copying down" a couple of rows and see if more dramatic retarding of the cams at higher RPM helps.

The VVT funcionality in the LH2 (and LC3) came from the high feature V6s, and tuners found hp by modifying the VVT calibration in the LLT/LFX. That makes me think there is some hp to be gained here as well.

 

[lextoy]

thx for the responses!
i guess i was implying that with the top down and higher CD, if that reduced airflow thru the engine compartment due to being less efficient?
less airflow = hotter engine, hotter intake temps, less air intake due to reduced pressure.
probably all negligible since air is ramming in thru the front and would only get turbulent aft of the windshield.
i am stuck postulating this low level stuff because there is no way i can form a coherent thought on the tuning part you are working on!!
i can follow your thought process because you explain it very well, but forging new ideas... hmmm i'm not at that level !
i bet if you design a high performance tune, theres a bunch of base model XLR owners that would pay to have it, i know i would.

 

[lextoy]

i totally agree volant is providing cooler charge as air spends alot less time in the intake tract.
i think i read somewhere there are some panels btw the grill and cone filters that can be removed to allow for even better airflow into engine compartment.
update: looks like it was on the V but may still apply to the base...
https://www.xlr-net.com/forums/cadi...-and-n-air-filter.html?highlight=grill+volant

do you intend to do any engine mods?valve springs, intake porting or full swap?
you know the potential in a SC, you have one ! sadly nothing much available for the LH2's
apparently theres quite alot of off road sand-rail guys who like the northstars
but i think they were modding slightly older engines than ours.
i could never find much info.

 

[lextoy]

wow everything i ever learned about the LH2, you already knew in 2009...
LH2 | CaddyInfo – Cadillac Conversations Blog

fyi, after reading this i recall a tuner, chuck @ CoW, corvettes of west chester, NY
claims to be able to program the electronic throttle to be more responsive...
does it make more HP?? nope.
but it does make sense to snap the throttle open quicker for more peppy performance.
sadly , once again my contribution is very weak, but hopefully informative

 

[lextoy]

from wikipedia...
why does the LH2 have more torque in the srx and sts ?? just slightly different tune?
[h=3]LH2[edit][/h]The Northstar was designed originally for transverse front-wheel drive applications. It was modified substantially in 2004 for longitudinal rear- and all-wheel drive use in the STS, SRX, andXLR, as well as receiving continuously variable valve timing on both intake and exhaust sides. The RWD (LH2) Northstar produces 320 hp (239 kW) and 315 lb·ft (427 N·m). An increased compression ratio of 10.5:1 enables most of the increase in power from the L37 and LD8 Northstars.
[TABLE="class: wikitable"]
<tbody>[TR]
[TH="bgcolor: #F2F2F2, align: center"]Year[/TH]
[TH="bgcolor: #F2F2F2, align: center"]Model[/TH]
[TH="bgcolor: #F2F2F2, align: center"]Power[/TH]
[TH="bgcolor: #F2F2F2, align: center"]Torque[/TH]
[/TR]
[TR]
[TD]2004–2009[/TD]
[TD]Cadillac SRX[/TD]
[TD]320 hp (239 kW) @ 6400 rpm[/TD]
[TD]315 lb·ft (427 N·m) @ 4400 rpm[/TD]
[/TR]
[TR]
[TD]2004–2009[/TD]
[TD]Cadillac XLR[/TD]
[TD]320 hp (239 kW) @ 6400 rpm[/TD]
[TD]310 lb·ft (420 N·m) @ 4400 rpm[/TD]
[/TR]
[TR]
[TD]2005–2010[/TD]
[TD]Cadillac STS[/TD]
[TD]320 hp (239 kW) @ 6400 rpm[/TD]
[TD]315 lb·ft (427 N·m) @ 4400 rpm

[/TD]
[/TR]
</tbody>[/TABLE]

 

[Bwnunnally]

thx for the responses!
i guess i was implying that with the top down and higher CD, if that reduced airflow thru the engine compartment due to being less efficient?
less airflow = hotter engine, hotter intake temps, less air intake due to reduced pressure.
probably all negligible since air is ramming in thru the front and would only get turbulent aft of the windshield.
i am stuck postulating this low level stuff because there is no way i can form a coherent thought on the tuning part you are working on!!
i can follow your thought process because you explain it very well, but forging new ideas... hmmm i'm not at that level !
i bet if you design a high performance tune, theres a bunch of base model XLR owners that would pay to have it, i know i would.

I would not expect top up/down to have a significant effect on air flow to the engine -- the top is downstream of the airflow relative to the air intake so to speak.
If the XLR was more powerful with the top down that would make me smile though.

 

[Bwnunnally]

i totally agree volant is providing cooler charge as air spends alot less time in the intake tract.
i think i read somewhere there are some panels btw the grill and cone filters that can be removed to allow for even better airflow into engine compartment.
update: looks like it was on the V but may still apply to the base...
https://www.xlr-net.com/forums/cadi...-and-n-air-filter.html?highlight=grill+volant

do you intend to do any engine mods?valve springs, intake porting or full swap?
you know the potential in a SC, you have one ! sadly nothing much available for the LH2's
apparently theres quite alot of off road sand-rail guys who like the northstars
but i think they were modding slightly older engines than ours.
i could never find much info.

I have seen some air ducting or 'funnel' mods that help get air directed to the filters on other cars.
The factory engineers would not use the volant approach due to the chance of water intake while driving in a heavy rain -- I suspect it is not up to 'spec' in that regard.
I am mostly interested in the LH2 as a long-term project, so first to look and see low hanging fruit. I have the LC3 to play with in the STS-V, and I have another OEM supercharger on the shelf so that would be the natural bolt-on for the LH2. But I don't plan anything radical - I enjoy finding out more about the package and tuning.

 

[Bwnunnally]

wow everything i ever learned about the LH2, you already knew in 2009...
LH2 | CaddyInfo – Cadillac Conversations Blog

fyi, after reading this i recall a tuner, chuck @ CoW, corvettes of west chester, NY
claims to be able to program the electronic throttle to be more responsive...
does it make more HP?? nope.
but it does make sense to snap the throttle open quicker for more peppy performance.
sadly , once again my contribution is very weak, but hopefully informative

I think I looked at that in my calibration and the throttle was already immediately at 100% -- no ramp in on the opening rate.
You can reprogram the throttle so current 25% the engine sees as 35% or similar, but why not just press down further when you want more throttle?

 

[Bwnunnally]

from wikipedia...
why does the LH2 have more torque in the srx and sts ?? just slightly different tune?
LH2[edit]

The Northstar was designed originally for transverse front-wheel drive applications. It was modified substantially in 2004 for longitudinal rear- and all-wheel drive use in the STS, SRX, andXLR, as well as receiving continuously variable valve timing on both intake and exhaust sides. The RWD (LH2) Northstar produces 320 hp (239 kW) and 315 lb·ft (427 N·m). An increased compression ratio of 10.5:1 enables most of the increase in power from the L37 and LD8 Northstars.
[TABLE="class: wikitable"]
<tbody>[TR]
[TH="bgcolor: #F2F2F2, align: center"]Year[/TH]
[TH="bgcolor: #F2F2F2, align: center"]Model[/TH]
[TH="bgcolor: #F2F2F2, align: center"]Power[/TH]
[TH="bgcolor: #F2F2F2, align: center"]Torque[/TH]
[/TR]
[TR]
[TD]2004–2009[/TD]
[TD]Cadillac SRX[/TD]
[TD]320 hp (239 kW) @ 6400 rpm[/TD]
[TD]315 lb·ft (427 N·m) @ 4400 rpm[/TD]
[/TR]
[TR]
[TD]2004–2009[/TD]
[TD]Cadillac XLR[/TD]
[TD]320 hp (239 kW) @ 6400 rpm[/TD]
[TD]310 lb·ft (420 N·m) @ 4400 rpm[/TD]
[/TR]
[TR]
[TD]2005–2010[/TD]
[TD]Cadillac STS[/TD]
[TD]320 hp (239 kW) @ 6400 rpm[/TD]
[TD]315 lb·ft (427 N·m) @ 4400 rpm
[/TD]
[/TR]
</tbody>[/TABLE]

My guess would be the XLR was 'blessed' with the exhaust setup from the Vette which is not ideal. No idea if the intakes were the same or not -- I think we could examine the diagrams and see if there is something radically different there.